Across:
1 Works (HOLDS DOWN A JOB) to restrain (HOLD-) swindlers primarily ('Swindlers' primarily = -S) in Northern Ireland (DOWN) on a (A) criminal enterprise (JOB) (HOLDS DOWN A JOB),
10 Overuse (overuse) adaptation (= anagram indicator) (overuse = OEUVRES) of works (works = OEUVRES),
11 Split (split/tear = RIP-) institute (-I-) sets up (= reversal indicator) one (one = -ENO) (RIPIENO) group accompanying the concertino (RIPIENO group of instruments accompanying the concertino),
12 Created a sketch (DREW) that’s weird (weird) without single (i) (‘weird’ without ‘i’ = werd) backtrack (= reverse indicator) (werd = DREW),
13 Supports (HOLDS) more than one in 13 across (more than one ‘hold’ = HOLDS),
15 Clutch (HOLD) for those starting on the grid today (HOLD starting on all sides of the grid today),
17 Urgent call (SOS) from inside espresso shop (from inside ‘espresSO Shop’ = SOS),
19 Flipping (= reverse indicator) tip for answering (tip for ‘Answering’ = -A) first (-I-) time (-T-) in Winning Streak (run = NU-R-) (NUTRIA) produced by a beasty type (NUTRIA),
21 Small homely type (BEDSIT) of piece (bit = B-IT) about journalists (Eds = -EDS-) (BEDSIT),
22 Kelvin (-K-) and Mike (-M-) in Italian city (Milan = MIL-AN) (MILKMAN) – one needs a float to go to work? (MILKMAN),
23 Turns (= reverse indicator) up (up = PU-) in the middle of summit (middle of ‘suMMit’ = -MM-) joining the foreign (‘the’ foreign = EL) (PUMMEL) strike (strike/hit = PUMMEL),
25 Crossing Swords (crossing swords = fighting/ROWING) for sport witnessed by The Liffeysiders (those on the banks of the Liffey watching ROWING),
27 Careful to dismiss clue (‘careful’ to dismiss ‘clue’ = arf = FAR) from wide partner? (FAR and wide),
29 National flags on both sides (‘NAtional flaGS’ on both sides = NAGS) from Troubles (NAGS),
30 He’s out of whiskies (‘hes’ out of ‘whiskies’ = wiski = KIWIS) and fruits for cocktails, for instance (KIWIS),
31 Characters with no carers (‘characters’ with no ‘carers’ = hact = CHAT) or that’s the talk online (CHAT),
34 Gangster (-AL- Capone) taken in by jazz (= anagram indicator) lover (lover = OVER-L) (OVERALL), by and large (OVERALL),
35 Bar (-RAIL-) close to Lommel (close to ‘lommeL’ = -L-) in Belgium (B-E) (BRAILLE) – on paper, one can read a lot into it with feeling (BRAILLE),
36 H (H-) from Line of Duty leads (‘Line Of Duty’ leads = lod) corruption (= anagram indicator) (lod = -OLD) on a (A-) new (-N) investigation (INQUIRY) (HOLD AN INQUIRY) – get the judge to look into it (HOLD AN INQUIRY).
Down:
2 Palatial (OPULENT) Oxford (O-) bar (pub) is not finished (b) ('pub' without 'b' = -PU-) – is it time to give up? (-LENT) (OPULENT),
3 Sides of triangular pyramid (sides of ‘TRiangular pyramID’ = trid) built over (= reverse indicator) (trid = DIRT) topsoil (DIRT),
4 Panel discussion ignores peninsula (‘panel discussion’ ignores ‘peninsula’ = dscsio = DISCOS) with dance clubs (DISCOS),
5 Direction (West = W-) taken by warring (= anagram indicator) lords (lords = -ORLDS) (WORLDS) providing habitable environments for both natives and aliens (WORLDS),
6 Range (ALPS) of bass player (‘basS PLAyer’ = spla) making a comeback (= reverse indicator) (spla = ALPS),
7 It’s a troublesome task (ONEROUS) for Oscar (O-), being highly strung (nervous) losing vote (‘v’) (‘nervous’ losing ‘v’ = -NEROUS) (ONEROUS)
8 Keep in mind (HOLD AN OPINION) hotel (H-) is not modern (-OLD) and (and) is missing front deck (front ‘Deck’ = d) (‘and’ without ‘d’ = AN) with view (OPINION) (HOLD AN OPINION)
9 Doesn’t fall apart (HOLDS TOGETHER) as The Nelsons, for instance (“half-nelson” + “full nelson” = HOLDS in wrestling), joined United (TOGETHER) (HOLDS TOGETHER)
14 Depressed (low = LO-W) over poor (= anagram indicator) Jack (Jack = -CKJA-) (LOCKJAW) getting tetanus (LOCKJAW),
16 Pay (pay = remit) back (= reversal indicator) (remit = TIMER) for track official (TIMER),
18 Baritones disregard bias (‘baritones’ disregard ‘bias’ = rtone = TENOR) of male singer (TENOR),
20 Trouble (AIL) catching up (= reverse indicator) in Parliament (in ‘parLIAment’ = lia = AIL),
21 Space on the keyboard (space BAR) to play a tune (play a BAR),
24 Small electric generator (MAGNETO) with a (-A-) great (-G-) catch (-NET-) found in Missouri (MO = M-O) (MAGNETO),
26 Trendy (IN-) hot (-H-) drink (-ALE-) to go with ultimate starter (ultimate ‘starteR’ = -R) (INHALER) – handy for anyone who needs a breather (INHALER),
27 Step into someone’s boots (FILL IN) almost (g) providing help for restoring The Crown? (‘filling’ without ‘g’ = fillin = FILL IN),
28 Fair prize (fair prize = RIBBON) for absorbing the release of gas (‘absorbing’ without ‘gas’ = borbin = RIBBON),
32 Staff (staff/stick = WAND) from magician’s bar (bar/stick = WAND),
33 The neighbour’s (the neighbours = UK = -KU) leaders assisting banks (leaders ‘Assisting Banks’ = ab) all up (= reverse all indicator) (ab = BA-) (BAKU) in The Capital (BAKU).