Across:
1 Short (e) prison term ('time' without 'e' = TIM-) for graduate (-BA-) taking large (-L) (TIMBAL) old kettledrum (TIMBAL),
4 Masters (Dutch masters = DUTCHMEN) European language (DUTCH-) for workers (-MEN) (DUTCHMEN),
9 Pulse (LENTIL) lost (L-) leader of Triads (leader of ‘Triads’ = -T-) in line- (line) -up? (= reversal indicator) (line = -EN-IL) (LENTIL),
10 Most of (t) the component (‘part’ without ‘t’ = PAR-) from Oxford (-O-) stops working (-DIES) (PARODIES) with apes (apes/skits = PARODIES),
12 Unimaginative (FORMULAIC) Lucia from (Lucia from) Knock? (= anagram indicator) (Lucia from = FORMULAIC),
13 Give one’s consent to (AGREE) set up (= reverse indicator) part of Vermeer gallery (set up part of ‘vermEER GAllery’ = eerga = AGREE),
14 Order (-O-) good books (Old Testament = -OT-), by European (POLISH-) in Belgium (BE = B- -E-), for reading (-R) (BOOT POLISHER) to the one responsible for taking a shine to Brogan (taking a shine to a brogan/shoe = BOOT POLISHER),
18 Particular (particular = HARD TO PLEASE) type of convertible (hardtop = HARD TO P-) for hire (-LEASE) (HARD TO PLEASE),
21 Love (ADORE) what’s found in bread? Oregano! (what’s found in ‘breAD OREgano’ = ADORE),
22 Note (music note = -D-) on high flyers (-RAF-) found in plain-to-see (overt = OVER-T) (OVERDRAFT) bank facility (OVERDRAFT),
24 Keep under control (RESTRAIN) with Cross (= anagram indicator) Trainers (trainers = RESTRAIN),
25 I’ve left again over (‘Ive’ left ‘again over’ = aganor = ANGORA) source for wool (ANGORA goat or rabbit),
26 Challenges (CONTENDS) to opening commercial (opening ‘Commercial’ = C-) broadcast (-ON-) for ministers (-TENDS) (CONTENDS),
27 Temporary occupant (LESSEE) of port (port/left = L-) city in Germany (Essen) hasn’t finished (n) (‘Essen’ without ‘n’ = -ESSE-) engineering (-E) (LESSEE).
Down:
1 Break the news to (TELL) FBI (FBI) boss (= anagram indicator) (FBI = FIB-) leading search (leading 'Search' = -S) (TELL FIBS) for lies (TELL FIBS),
2 Ms Monroe (Ms Monroe) dancing (= anagram indicator) (Ms Monroe = MEN’S ROOM) with the gents (MEN’S ROOM),
3 Delta (-D-) that is (i.e. = -IE-) in Australia (AU = A-U) (ADIEU) and so long (so long = ADIEU),
5 Not used to (UNACCUSTOMED to) a French (‘a’ French = UN-) Academy (-A-) around (= reverse indicator) December (Dec = -C-ED) holding Convention (-CUSTOM-) (UNACCUSTOMED),
6 Prepare dinner (COOK A MEAL) with endless (l) fashionable (cool) (‘cool’ without ‘l’ = COO-) Egyptian spirit (Ka = -K A) to go with edible part of grain (MEAL) (COOK A MEAL),
7 Trim (d) hotel worker (‘maid’ without ‘d’ = MAI-) picks up (= reverse indicator) bit of work (erg = -GRE) (MAIGRE) from one of those fast types, eschewing meat (MAIGRE),
8 Made a home (NESTED) out of necessity (NE-ED) across the street (-ST-) (NESTED),
11 Got a call from creche owner to look after children (CALLED TO MIND) and that’s not forgotten (CALLED TO MIND),
15 Sounds like (= homophone indicator) vanilla (‘plain’ = ‘PLANE’) with cherry (TREE) (PLANE TREE) – typically ordered along the road entering a French town (PLANE TREE),
16 Turns up (= reverse indicator), Kiss (snog = -GONS) is associated with a (-A-) type of music (rap = PAR-) (PARAGONS) produced by the perfect models (PARAGONS),
17 What The Sun’s fans are looking for (HEATWAVE) leads to local pressure from police department (local ‘pressure’ = HEAT) to renounce (waive) report? (= homophone indicator) (‘waive’ = ‘WAVE’) (HEATWAVE),
19 Francis Bacon dismisses canons (‘Francis Bacon’ dismisses ‘canons’ = fracib = FABRIC) manipulated by the man of the cloth (FABRIC),
20 Ease up on (LOOSEN) salad (= anagram indicator) on sole (on sole = LOOSEN),
23 Harm from hand cream (‘harm’ from ‘hand cream’ = ndcea = DANCE) – that’s the twist? (DANCE).