Across:
1 Flipping (= reverse indicator) crafty type (ship = SS= -SS) on Elba (Elba) replaces novice (learner = 'l') with bishop ('b') (in 'elba', replace 'l' in with 'b' = ebba = ABBE-) (ABBESS) – the one running convent (ABBESS),
4 “Caught (-C-) in Ocean Liner (ocean liner = sand = S-AND-) with Gangsters” (gangster’s /Al Capone’s = -ALS) (SCANDALS) – the headlines in the tabloids (SCANDALS),
9 Small (S-) sheets of paper (-QUIRE) (SQUIRE) produced by Sancho Panza, for one (SQUIRE),
10 The Cure (MEDICINE) working in theatre (MEDIC-) in (-IN-) Spain (-E) (MEDICINE),
12 Given a wide berth (LEFT ALONE) in Split (LEFT) on one’s own (ALONE) (LEFT ALONE),
13 A large unruly crowd (HORDE) from State (= homophone indicator) put away for a long time (‘hoard’ = ‘horde’ = HORDE),
14 Teach the guards how to work Pulse presumably (train Garda station = TRAIN STATION) in Kent, for instance? (Kent TRAIN STATION in Cork),
18 One of those employed in pizzeria to cut down on the Parmesan (CHEESE GRATER) – Pecorino (CHEESE) is better (grater) we hear (= homophone indicator) (‘greater’ = ‘grater’ = GRATER (CHEESE GRATER),
21 Standard (USUAL) of university (-U-) in America (USA = US-A-) close to port (port/left = -L) (USUAL),
22 Clears out (EVACUATES) part of the roof (eaves) said (= homophone indicator) (‘eaves’ = ‘eves’ = EV-ES) to include area (-A-) with copper (-CU-), leads, aluminium, tin (leads/first letters of ‘Aluminium Tin’ = -AT-) (EVACUATES),
24 1,000 (-M-) at university (University of Limerick = -UL-) consumed by cacophony (noise) – “Up (= reverse indicator) (noise = E-SION) (EMULSION) Mayo!” (mayonnaise = EMULSION),
25 Upsets (= reverse indicator) a (-A) group of workers (men = -NEM-) in charge (IC = CI-) (CINEMA) of producing the pictures (CINEMA),
26 What Angus (bull) is bound to look through (BULL’S EYE) is sweet (BULL’S EYE sweet),
27 Serves (serves) soup (= anagram indicator) (serves = VERSES) to a number of those in Limerick (limerick VERSE).
Down:
1 Beau lost (beau lost) out (= anagram indicator) (beau lost = ABSOLUTE), as there's no other option (ABSOLUTE),
2 Beluga (Beluga = BLUE -AG) swimming (= anagram indicator) around Florida (FL-) (BLUE FLAG) – it’s a sign of a clean beach (BLUE FLAG),
3 Well-ventilated (airy = -YRIA) restaurants finally (‘restaurantS’ finally = = S-) set up (= reverse indicator) (SYRIA) in the country (SYRIA),
5 Had words (CHEWED THE FAT) with revolutionary (CHE-) getting to form a union (form a union = WED) for most of them (most of ‘them’ = THE) from Greece (Greece) we hear (= homophone indicator) (‘Greece’ = ‘grease’ = FAT) (CHEWED THE FAT),
6 Region, hub (region hub), settlement (= anagram indicator)? (region hub = NEIGHBOUR) One of them is presumably on next door’s doorstep! (NEIGHBOUR),
7 A (A-) park (-P-) leads in all respects (leads ‘In All Respects’ = -IAR-) to yard (-Y) (APIARY) in Queen’s home (beehive = APIARY),
8 Resist leaving dessert wines (‘resist’ leaving ‘dessert wines’ = deswne = SWEDEN) in Scandinavia (SWEDEN),
11 Use track (JOG) with recurring melody (theme = THE ME-) on both sides of Morning Glory (on both sides of ‘MOrning gloRY’ = -MORY) (JOG THE MEMORY) to aid recall (JOG THE MEMORY),
15 Popular (in) revolutionary (= reverse indicator) (in = NI-) going to joint (hip joint) endlessly (p) (‘hip’ without ‘p’ = -HI-) for overseas tips (overseas tips/boat leans over = -LISTS) (NIHILISTS) from extreme sceptics (NIHILISTS),
16 Half the cast (half the ‘caST’ = ST-) puts into words (-UTTERS) (STUTTERS) or fluffs the lines? (STUTTERS),
17 Turn on the waterworks (CRY-) for last (last) shift (= anagram indicator) (last = -STAL-) producing endless (end ‘lesS’ = -S) (CRYSTALS) pieces of cut glass (CRYSTALS),
19 Romanian neighbour (Serb = S-ERB) admits taking top off (c) trophy (‘cup’ without ‘c’ = -UP-) (SUPERB) and smashing? (SUPERB),
20 Joint (MUTUAL) found in The Lautumiae (found in ‘the LAUTUMiae’ = lautum) going all the way back (reverse indicator) (lautum = MUTUAL),
23 Ally (UNITE) is out of line ignoring fool (‘out of line’ ignoring ‘fool’ = utine = UNITE).