Across:
8 What’s required for 2 down (POTATO required for ‘mash’) and one of the records (one of the records = variety of POTATO),
9 Maintain (PRESERVE) park (P-) for one of those on bench (extra player/sub on bench = -RESERVE) (PRESERVE),
10 Drop a line (FISH) to half of those in 3 down (half of ‘monkFISH’ = FISH),
11 Swimmers, synonymous with smoking (KI-PPERS), harbouring genetic information (-DNA-) (KIDNAPPERS), seeking compensation after a seizure (KIDNAPPERS),
12 Rogue (SCAMP-) from island (-I) (SCAMPI) is caught in the sea swimming (SCAMPI),
14 Boss (= anagram indicator) retires (retires = RE-ISTER) over Golf (-G-) (REGISTER) Lodge (lodge/submit = REGISTER),
15 Local records (PARISH REGISTERS) with a type of music (rap = PAR-) backtrack (= reverse indicator) is (-IS-) hot? (-H) With 14 across (‘register’ = REGISTER-), it’s close to glorious! (close/end to ‘gloriouS’ = -S) (PARISH REGISTERS),
18 Relative (uncle = UN-CLE) admits being far from friendly (-ICY-) (UNICYCLE) with one of those taken for a ride by a clown (UNICYCLE),
20 Raised (= reverse indicator) crafty type (SS = S-S) hiding criminal leader? (Don = -NOD-) Yes (-Y-) (SYNODS), in church gatherings! (SYNODS),
22 It’s a preference of mine (MY CUP OF TEA) to take it personally with biscuits at break time? (MY CUP OF TEA).
24 Brother (MONK) to a fair of amount of (half of) the characters in 3 down (half of ‘MONKfish’ = MONK),
25 Oscar (O-) denies (denies) adaptation (= anagram indicator) (denies = -NE-SIDE-) is primarily discriminatory (primarily ‘Discriminatory’ = -O) (ONE-SIDED) or lacking in balance (ONE-SIDED),
26 Way out (way out/path = COURSE) of 13 down at last (‘main course’ at last = COURSE).
Down:
1 Nothing (-O-) in Cadiz (Cadiz = Z-DIAC) works (= anagram indicator) (ZODIAC) – so much for those making predictions? (ZODIAC),
2 Leads for microphones and sophisticated headphones (leads for ‘Microphones And Sophisticated Headphones’ = MASH) produced by Pulp (MASH),
3 One of those in The Abbey (MONK-) cast (-FISH) (MONKFISH) is on a seafood diet (MONKFISH).
4 To the locals, The Duke of York (local ‘the Duke of York potato’ = SPUD) is similar to 8 across (SPUD is similar to ‘potato’),
5 Dress (= anagram indicator) hanger (hanger = REHANG) is put back in the closet (REHANG),
6 11+12+13+14+15+16+17+18+19+20 (10 numbers after/past ten = TEN PAST TEN) 1,010? (10.10pm = TEN PAST TEN),
7 Catch (catch/overhear = OVERHEAR) report (= homophone) of GIs in Britain during the war, as the saying goes (comedian Tommy Trinder’s catchphrase: “overpaid, oversexed, overfed and over here” = “over here” = “OVERHEAR”),
13 Principal (MAIN) with links (golf links COURSE) (MAIN COURSE) to one of those coming out of the kitchen (MAIN COURSE),
14 Breaks even, ignoring bank’s (‘breaks even’ ignoring ‘banks’ = reeve = REEVE) local official in the past (REEVE),
16 Woman (ANN) and young man (boy) scratching head (b) (‘boy’ without ‘b’ = -OY-) in (-IN-) Government (-G) (ANNOYING) getting on someone’s nerves (ANNOYING),
17 Typical case (example = INSTANCE) of popular (IN-) attitude (-STANCE) (INSTANCE),
19 It’s not clear (CLOUDY) cook (= anagram indicator) could (could = CLOUD-) finish pastry (finish ‘pastrY’ = -Y) (CLOUDY),
21 Is rather sweet during the break (DANISH pastry) describing Hamlet (DANISH),
23 Ross gets off steroids (‘Ross’ gets off ‘steroids’ = teid = TIDE) – the current trend suggesting it has a yo-yo effect (yo-yo effect = TIDE),
24 Serving up (= reverse indicator) some Kahlua mudslide (some ‘kahLUA Mudslide’ = luam = MAUL) for local bash (local ‘bash’ = maul – MAUL).