Across:
8 Hemingway ignores why (‘Hemingway’ ignores ‘why’ = eminga = ENIGMA) this is hard to fathom (ENIGMA),
9 Officer (Officer Commanding = OC-) from Sergei Prokofiev’s War and Peace, for instance (aria = -ARI-A-), protecting Napoleon (-N-) with endless (end ‘lesS’ = -S) (OCARINAS) instruments (OCARINAS),
10 Rushed off one’s feet (BUSY) by us (by us) moving (= anagram indicator) (by us = BUSY),
11 Best tutu is (best tutu is) designed (= anagram indicator) (best tutu is = SUBSTITUTE) as a replacement (SUBSTITUTE),
12 Iron (FE = F-E-) over mistake (-ERR-) and initial trouble (initial ‘Trouble’ = -T) (FERRET) or dig up? (FERRET),
14 Greek island (RHODES-) is initially (‘Is’ initially = -I-) in touch with academy (-A) (RHODESIA) in old African territory (RHODESIA),
15 Alien (-ET) abode in the sticks (CABIN-) opened (= position indicator) by father (MINISTER) (CABINET MINISTER) of government official (CABINET MINISTER),
18 Legend (‘leG’ end = G-) gets nothing from tennis (-LOVE-), from fight in the ring (-BOX in the boxing ring) (GLOVEBOX) or from one of the handy types in golf (handy type in VW Golf car = GLOVEBOX),
20 Cool (MODISH) microwave oven starters (‘Microwave Oven’ starters = MO-) served up by restaurant (-DISH) (MODISH),
22 Part of the ground (STAND) for the defender (GUARD) (STAND GUARD) to keep an eye on (STAND GUARD),
24 First mate has no taste (‘first mate’ has no ‘taste’ = firm = FIRM) for company (FIRM),
25 English (-E-) workers (-MEN-) in outside accommodation (tent = TEN-T) (TENEMENT) by old rundown housing unit (TENEMENT),
26 Where in France (French ‘where’ = OU-) Disney (Walt) set up (= reversal indicator) (Walt = -TLAW) (OUTLAW) bar (bar/ban = OUTLAW).
Down:
1 Cover (INSURE) for one (I-) sick (= anagram indicator) nurse (nurse = -NSURE) (INSURE),
2 Lay figure puts out a fire (‘lay figure’ puts out ‘a fire’ = lygu = UGLY) that’s not much to look at (UGLY),
3 Video (video CASSETTE) most of the cast (‘cast’ without ‘t’ = CAS-) on couch (settee) – the last one is missing! (e) (‘settee’ without ‘e’ = -SETTE) (CASSETTE),
4 Relative (mom) loses the head (m) (‘mom’ without ‘m’ = -OM-) inside the hostelry (B&B = B-B) (BOMB) in Blitz (BOMB),
5 Philosophy (Tao = TA-O) about race (-TT- race) origins initially (‘Origins’ initially = -O-) (TATTOO) will leave its mark (TATTOO),
6 Misery (DISTRESS-) writer (-ED) (DISTRESSED) is tormented (DISTRESSED),
7 Not mad (sane = SA- -NE) about soldier (lieutenant = -LT) on road (MI = MI-) (SALT MINE) leading to place of hard labour synonymous with one of the seasons (SALT MINE),
13 Made up again (REINVENTED) by popular (-IN-) outlet (-VENT-) with a fair amount of grass on either side (reed = RE-ED) (REINVENTED),
14 Extremists dismiss tests (‘extremists’ dismiss ‘tests’ = xremi = REMIX) as a DJ’s creation (REMIX),
16 Assigned (ALLOTTED) a good deal (-LOT-) in flourishing (= anagram indicator) Delta (Delta = AL-TED) (ALLOTTED),
17 Mention famous friends (NAMEDROP) finishing (= position indicator) with a Bandon (abandon = -DROP) Dub? (dub/give a name = NAME-) (NAMEDROP),
19 A ringer (BIG BEN) for Westminster belle (Westminster belle) on the radio (= homophone indicator) (Westminster ‘belle’/ Westminster ‘bell’ = BIG BEN),
21 A steady flow (STREAM) from master (master) criminal (= anagram indicator) (master = STREAM),
23 Pretentious type (ARTY) of banks from Arkansas City (banks from ‘ARkansas ciTY’ = ARTY),
24 Fundraiser (FETE) gets rash from feathers (‘rash’ from ‘feathers’ = fete = FETE).