Across:
1 Serves up (= reverse indicator) lentil (puy lentil = puy = -Y-UP-) recipe (-R-) in the middle of party (Sinn Féin = SF = F-S) (FRY-UPS) with lots of bacon, sausage and egg (FRY-UPS),
4 It’s a revelation (EPIPHANY) to one with great expectations (-PIP- is the one with great expectations in Charles Dickens’ Great Expectations) trapped by wild (= anagram indicator) hyena (hyena = E-HANY) (EPIPHANY),
9 They keep an eye on the offspring (ADULTS) of mature animals (ADULTS),
10 Spirit (ARMAGNAC) to unravel (= anagram indicator) anagram (anagram = ARMAGNA-) – that’s key (music key -C) (ARMAGNAC),
12 Heads on beer in Gloucestershire (heads on ‘Beer In Gloucestershire’ = BIG) and Cheshire (Cheshire CHEESE) (BIG CHEESE) produced by the main man (BIG CHEESE),
13 Give out (ALLOT) to OAP from Palo Alto (‘OAP’ from ‘Palo Alto’ = lalto = ALLOT),
14 Part of study – to a certain degree (DISSERTATION), one has to defend it, of course (defend DISSERTATION/thesis via viva voce),
18 Oasis (WATERING HOLE), managed by one behind bars? (WATERING HOLE managed by one behind bars/public houses),
21 Part of the statue (TORSO) found in doctor’s office (found in ‘docTORS Office’ = TORSO),
22 I did it (I did it = SUCCESS-) at Oxford (-O-) writing (from the 3Rs = -R) (SUCCESSOR) to heir apparent (SUCCESSOR),
24 Keep an eye out for Labour (FIND A JOB) offering to take another’s position (FIND A JOB),
25 The bishop’s place (see = S-EE-) overlooking front of parish (front of ‘Parish’ = -P-) church (-CH) (SPEECH), in a manner of speaking (SPEECH),
26 Showed a documentary (SCREENED) of Partition (SCREEN-) by writer (-ED) (SCREENED),
27 Shock waves (BLASTS) from cabalists dismissing CIA (‘cabalists’ dismissing ‘CIA’ = ablsts = BLASTS).
Down:
1 Accommodation (FLAT-) with lots of furniture (-BEDS) (FLATBEDS) for those in the haulage business (FLATBEDS),
2 The issue (YOUNG-) with his (his) novel (= anagram indicator) (his = -ISH) (YOUNGISH) – it’s slightly immature (YOUNGISH),
3 Sales talk (PITCH) to those characters at the end of 5 down (those characters at the end of ‘perfect pitch’ = PITCH),
5 An asset to someone in a jam (an asset to someone in a jam/music session = PERFECT PITCH) is appreciated by the best footballers (PERFECT PITCH),
6 Pretend to cooperate (PLAY ALONG) by beach in Malaga (playa = PLAY A-) and record musings (record musings = log = -LO-G) about One Direction (North = -N-) (PLAY ALONG),
7 Girl (ANNA-) left (-L-) school (-S) (ANNALS) with historical records (ANNALS),
8 Cathy’s (Cathy’s) all at sea (= anagram indicator) (Cathys = YACHTS) in pleasure crafts (YACHTS),
11 Arrange (SETTLE) American (A) music for film (SCORE) (SETTLE A SCORE) to pay someone back (SETTLE A SCORE),
15 The foreign (the = EL-) sailor (Able-Bodied seaman = -AB-) meets old (-O-) judge (-RATE) (ELABORATE) to flesh it out (ELABORATE),
16 Ships (cargo ships = COASTERS) most of (d) fish (‘cod’ without ‘d’ = CO-) for Daisy’s relatives (-ASTERS) (COASTERS),
17 Looks for (SEARCHES) her cases (her cases) all over the place (= anagram indicator) (her cases = SEARCHES),
19 Crook’s (crooks/croziers = STAFFS) party (Sinn Féin = SF = -FS) has chunky (fat = -TAF-) chips on the side (‘chipS’ on the side = S-) with everything served up (= reverse all indicator) (STAFFS),
20 Gets Holly back into shape (PRUNER) by cutting back on the Chardonnay? (cutting back on the Chardonnay grape = PRUNER),
23 Knocks back (= reversal indicator) Pedro Ximenez (PX = -XP-) in Irish river (River Lee = E-EL) (EXPEL) bar (bar/ban = EXPEL).