Across:
8 You and I (us) review (= reversal indicator) (us = SU-) party (-DO-) for returning (= reversal indicator) neighbours (UK = -KU) (SUDOKU) – the difficulty is getting the numbers right (SUDOKU),
9 Get to (RE-ACH) cover short business-like (professional = -PRO-) (REPROACH) lecture (lecture/reprimand = REPROACH),
10 One of those in the Mallow family (OKRA) removing plantain from national park (removing ‘plantain’ from ‘national park’ = oark = OKRA),
11 Great (G-) Dublin back (‘dubliN’ back = -N-) consumed by shocking (= anagram indicator) standard (standard = -RANDSTA-D) (GRANDSTAND) seen in Croke Park (GRANDSTAND),
12 State (OREGON) of REM leaving green room (‘REM’ leaving ‘green room’ = genroo = OREGON),
14 The Spanish- (LAS-) -American (-A-) sang (sang = -GNAS) backtrack (= reverse indicator) (LASAGNAS) coming out of Italian restaurant (LASAGNAS),
15 Comment (OBSERVATION) from The Mail (the mail = POST) (OBSERVATION POST) offering a general view perhaps (offering army general view / OBSERVATION POST)
18 College (C-) at the end of term (end of ‘terM’ = -M-) in Arabian country (Oman = -OM-AN-) has party (-DO) (COMMANDO) for one going on The Missions (COMMANDO),
20 Try to mediate (STEP IN) introducing some (introducing ‘Some’ = S-) inept (inept = -TEP IN) boss (= anagram indicator) (STEP IN),
22 Ref (ref) flicks over (= reverse indicator) (ref = F-ER) old (-O-), good books (Old Testament = -OT-) kicked about by striker (-BALL-) (FOOTBALLER) or forward (FOOTBALLER),
24 Supports without spur (‘supports’ without ‘spur’ = pots = POTS) in greenhouse containers (POTS),
25 Costly (STEEP-) for the French (the = -LES) (STEEPLES) types over places of worship (STEEPLES),
26 Infusion from nuclear fission (‘infusion’ from ‘nuclear fission’ = clears = CLEARS) melts away (CLEARS).
Down:
1 Shelter (BUNKER) from what the swingers hope to avoid (swingers/golfers hope to avoid BUNKER),
2 Work schedule (ROTA) is revolutionary (= reverse indicator) inside sanatoriums (inside ‘sanATORiums’ = ator = ROTA),
3 Press (-URGE-) in outlet (vent = T-NEV) upsets (= reverse indicator) (TURGENEV) writer responsible for a sportsman’s sketches (TURGENEV wrote A Sportsman’s Sketches),
4 Song (ARIA) from Avatar I appreciated (from ‘avatAR I Appreciated’ = ARIA),
5 Passed (passed) out (= anagram indicator) (passed = SPADES) in black suits (black suits/cards = SPADES),
6 Traditional fare (COTTAGE PIE) in accommodation (COTTAGE) for most those in 24 down (most ‘pies’ = PIE) (COTTAGE PIE),
7 Top cobbler (top ‘Cobbler’ = -C-) in footwear (S-ANDALS) (SCANDALS) with skeletons in the closet (SCANDALS),
13 Colourful type (GREY) from major hospital (Mater Hospital) spoke out (= homophone indicator) (‘Mater’ = ‘MATTER’) (GREY MATTER’) with intelligence (GREY MATTER),
14 Fire (LET GO) in accommodation (LET) starts gas oven (starts ‘Gas Oven’ = GO) (LET GO),
16 Depressed (-LOW-) in fights (bouts = B-OUTS) (BLOWOUTS) when the wheels come off? (BLOWOUTS),
17 CBS tutor (CBS tutor) drunk (= anagram indicator) (CBS tutor = OBSTRUCT) in bar (bar/block = OBSTRUCT),
19 Pole (North Pole = N-) is in good time (-EARLY) (NEARLY) or just about (NEARLY),
21 Keep under lock and key (INTERN), short academic test for older students (Intermediate Certificate = INTER-) at the end of examination (at the end of ‘examinatioN’ = -N) (INTERN),
23 Gloss over disappearing grove (‘gloss over’ disappearing ‘grove’ = loss = LOSS) – it’s a tax right-off (LOSS),
24 Torte from Potteries (‘torte’ from ‘potteries’ = pies = PIES) or from the bakery? (PIES).