Across:
8 No vista in Calvinistic (no ‘vista’ in ‘Calvinistic’ = clniic = CLINIC) medical centre (CLINIC),
9 One of those with bug (LISTENER) let siren (let siren = LISTENER) off (= anagram indicator),
10 Local crazy type (BATS) in combat ship (BATS in “combat ship”),
11 Sounds like advice from the director (DO YOUR PART) to party (DO) with ruffian (yob) heading off (y) (“yob” without “y” = YO-) to old city (-UR) section (PART) (DO YOUR PART),
12 Models (models = SELDOM) dress (= anagram indicator) once in a blue moon (SELDOM),
14 It’s the pugilist’s job (-BOX) to go after (= positional indicator) local money (BREAD-) (BREADBOX) or what’s left with the crumbs presumably (BREADBOX),
15 Diplomatic mission (AMERICAN EMBASSY) for us (US = AMERICA-) at the end of autumn (end of “autumn” = -N) in place of overseas reps (EMBASSY) (AMERICAN EMBASSY),
18 Conceal (SUPPRESS) sip (SUP-) from Squash (squash/crush = -PRESS) (SUPPRESS),
20 Place (LAY-) opens mid-August (opens/first letters of “mid August” = -MA-) with new head (“new” head = -N) (LAYMAN) who is not an expert (LAYMAN),
22 Takeaway (DETACH-) workers (-MEN-) find bone (-T bone) (DETACHMENT) in a part of 17 down (DETACHMENT unit/squad in the “military”),
24 Neighbours in the air (RAF-) on the first (“the” first = -T) (RAFT) transport overseas (RAFT),
25 Almost (d) not happy (“sad” without “d” = SA-) with Anselm (Anselm = LESMAN) travelling (= anagram indicator) (SALESMAN) with business agent (SALESMAN),
26 Religious leader (RABBI-) has a bone to pick (-T bone) (RABBIT) in The Warren perhaps (RABBIT).
Down:
1 Let out (-LEASE) pressure (P-) first (= positional indicator) (PLEASE), if you don’t mind (PLEASE),
2 Lose rag in garden’s (lose “rag” in “gardens” = dens = ENDS) borders (ENDS),
3 Educator (ACADEMIC) produced a (A-) computer-aided design (computer-aided design = -CAD-) to train (= anagram indicator) mice (mice = -EMIC) (ACADEMIC),
4 Sketch (short PLAY) parking (P-) place (-LAY) (PLAY),
5 Part of overseas sum employed (part of “overseas sum employed” = ASSUME) to take something on (ASSUME),
6 Don’t sell (KEEP) The Daily Record (A DIARY) (KEEP A DIARY) – is that what The Observer will do with The Daily News? (KEEP A DIARY),
7 Dreamy location (BED-) with accommodation (-ROOMS) (BEDROOMS) for retiring types (BEDROOMS),
13 Transportation system (DART) employed by the abbey (PLAYER in The Abbey) (DART PLAYER) is supposed to fit in 180 as often as possible (DART PLAYER),
14 Bars (BANDS) for the musical types (BANDS),
16 Mickey’s apartment perhaps (Mickey Mouse’s apartment = MOUSE PAD) has steady computer link (MOUSE PAD),
17 Forces (MILITARY) Mary (M-ARY) to take in one (-I-) that’s plastered (-LIT-) in a casual way (MILITARY),
19 Unearth (EXHUME) old partner (EX-) is a moral and political philosopher (moral and political philosopher (David -HUME) (EXHUME),
21 A (A-) party (Fianna Fáil = -FF-) broadcast (-AIR) (AFFAIR) leads to potential scandal (AFFAIR),
23 No grain in Argentina (no “grain” in “Argentina” = enta = ETNA) or Sicilian hot spot (ETNA),
24 Cloak (ROBE) the extremes of Robert Mugabe (the extremes of “Robert Mugabe” = ROBE).