Across:
8 Drink (BITTER) it (-IT-) with starter of toast (starter of ‘Toast’ = -T-) in Belgium (B-E-) at the end of summer (end of ‘summeR’ = -T) (BITTER),
9 Those from western vehicle perhaps (COACHMEN) providing Comanche (Comanche) action (= anagram indicator) (Comanche = COACHMEN),
10 Score (ETCH) heroin (-H) after (= position indicator) revealing a long list of others, in short (et cetera = etc. = ETC-) (ETCH),
11 Strategy explaining how the Leaving Cert will be done? (MASTER PLAN) And, that’s the best proposal you have! (MASTER PLAN),
12 Just look around (BROWSE) for prank from pawnbrokers (‘prank’ from ‘pawnbrokers’ = wboers = BROWSE),
14 Freudian slip with no puns (‘Freudian slip’ with no ‘puns’ = frediali = AIRFIELD) produced by JFK, the one in New York? (JFK airport in New York = AIRFIELD),
15 A level of frustration (DISSATISFACTION) is (-IS-) behind (= position indicator) dispute primarily (‘Dispute’ primarily = D-) for compensation (-SATISFATION) (DISSATISFATION),
18 It’s most important (DOMINANT) – don’t (don’t = DO-NT) take in short (i) dress (‘mini’ without ‘i’ = -MIN-) and top (‘And’ top = -A-) (DOMINANT),
20 Starting from here (starting from ‘Here’ = -H-) in confidence (trust = T-RUST) (THRUST) by barge (barge/push = THRUST),
22 What Adam has (GARDEN) stretched out (FLAT) (GARDEN FLAT) in a ground floor apartment (GARDEN FLAT),
24 Job in the theatre (PART) limits Patrick Stewart (limits ‘PAtrick stewaRT’ = PART),
25 Beer gave (beer gave) drunk (= anagram indicator) (beer gave = BEVERAGE) something to drink, other than water (BEVERAGE),
26 Lost the pounds (DIETED) and alms from Middle East (‘alms’ from ‘Middle East’ = iddeet = DIETED).
Down:
1 Conservatism is terrified internally (‘conservatisM IS TERrified’ internally = MISTER) by address (MISTER),
2 Pine (pine/itch = ITCH) or ivory twin heads (‘Ivory Twin’ heads = IT-) on taps? (Cold & Hot taps = -CH) (ITCH),
3 In the best shape (TRIMMEST) for trial (test = T-EST) over border (rim = -RIM-) in front of magistrate (in front of ‘Magistrate’ = -M-) (TRIMMEST),
4 Showcase who’s missing (‘showcase’ ‘whos’ missing = case = ACES) a great pair? (pair of ACES in poker),
5 Calling (vocation = CAREER) mercenaries to abandon mines (‘mercenaries’ to abandon ‘mines’ = ercear = CAREER),
6 Inform on local (inform on ‘locally’ = SHOP-) strongman (-LIFTER) (SHOPLIFTER) presumably taking stock (SHOPLIFTER),
7 Switches (= reverse indicator) oil (oil = -LIO) and gas (gas = S-AG-) flowing over reconnected electric leads (‘Reconnected Electric’ leads = re = -ER-) (SERAGLIO) in old apartments for women (SERAGLIO),
13 Direction (WEST) taken by cool (IN-) detectives (DIs = -DI-S) coming across ecstasy (-E-) (WEST INDIES) from Caribbean islands (WEST INDIES),
14 Advantage (ASSET) of setting out (= anagram indicator) seats (seats = ASSET),
16 Scares off leaders (‘Scares Off’ leaders = -SO-) and others (et al) turning up (= reverse indicator) (et al = -LATE-) in the papers (ID papers = I-D) (ISOLATED) for one of those lonely types (ISOLATED),
17 Update it (update it) employing (= anagram indicator) (update it = APTITUDE) natural ability (APTITUDE),
19 Once a year (ANNUAL) idealists leave Aleutian Islands (‘idealists’ leave ‘Aleutian Islands’ = uanlan = ANNUAL),
21 A number of waves (SERIES) sound (= homophone indicator) terrifying (‘eerie’ = ‘erie’ = -ERIE-) in boat (S-S) (SERIES),
23 Ran away from Ireland (‘ran’ away from ‘Ireland’ = ield = LIED) or Cork (LI-D) over sweetheart (‘swEet’ heart = -E-) (LIED),
24 Speak up for the man upstairs (pray) on the radio (= homophone indicator) (‘pray’ = ‘PREY’) in game (game/wild animals = PREY).