Across:
8 Regiment (R-) in the end (= positional indicator) finds wild (= anagram indicator) myth (myth = YTHM) initially hard (initially ‘Hard’ = -H-) (RHYTHM) to beat (RHYTHM),
9 Serves food to go (CHIP SHOP) with 24 across (‘chip’ = CHIP) and 23 down (‘shop’ = SHOP) (CHIP SHOP),
10 Central to Franz Josef I shaping (central to ‘franz joseF I SHaping’ = FISH) angle (FISH),
11 Out of date (RETRO-) letter from teacher after examination (letter: A, B, C ... is the -GRADE) (RETROGRADE) is in verse? (inverse = RETROGRADE),
12 Those ground-breaking types (SPADES) of accommodation (-PAD-) with key (music key -E-) in ship (S-S) (SPADES),
14 Ran around like a headless chicken (PANICKED) as father (PA-) got picked up by the guards locally (-NICKED) (PANICKED),
15 Take away (FISH AND CHIP SHOP) from 10 across (‘fish’ = FISH) as well as (AND) 9 across (‘chip shop’ = CHIP SHOP) (FISH AND CHIP SHOP),
18 Rewrite (= anagram indicator) grey tome (grey tome = GEOMETRY) for maths class (GEOMETRY),
20 Ross leaves Dusseldorf (‘Ross’ leaves ‘Dusseldorf’ = dueldf = FUDDLE) in state of confusion (FUDDLE),
22 Tablet (STONE-) is for two family members (ma + son= MASON) (STONEMASON) and one of the chisellers (STONEMASON),
24 Note (music note C-) in Vogue (-HIP) (CHIP) held by gambler (CHIP),
25 Latest (latest = -ALSETT-) sacking (= anagram indicator) in foreign office (Foreign Office = F-O) (FALSETTO) is off the scale and everyone will hear about it (FALSETTO),
26 Half suppressed laugh (TITTER) from Troy (T-) getting beer (bitter) with no head (‘bitter’ without ‘b’ = -ITTER) (TITTER).
Down:
1 Sister (Sr = S-R-) protects top of head (top of ‘head’ = -H-) from devilish creature (-IMP) (SHRIMP) swimming in the sea (SHRIMP),
2 Longing (ITCH) to head off (p) to the ground (‘pitch’ without ‘p’ = ITCH),
3 Turns up (= reverse indicator), no (no = -ON) teacher (sir = -RIS-) has heads probably messing indoors (heads ‘Probably Messing Indoors’ = pmi = IMP-) (IMPRISON) put in detention (IMPRISON),
4 Piece of Tangüis cotton (piece of ‘tangüiS COTton’ = SCOT) synonymous with Paisley (Paisley town in Scotland / SCOT),
5 Turn one’s back on (DISOWN) Shaw getting out of sash window (‘Shaw’ getting out of ‘sash window’ = sindow = DISOWN),
6 Loses the head (p) with tweet (‘post’ without ‘p’ = OST-) brought up (raised = -RA-ISED) about college (-C-) (OSTRACISED) that’s blacklisted (OSTRACISED),
7 Into the bargain (TOO-), lost (= anagram indicator) dole (dole = -DLE-O-) at job centre? (centre of ‘jOb’ = -O) (TOODLE-OO) That’s some parting shot! (TOODLE-OO),
13 Cast aspersions on the sociability of (DEHUMANISE) person (-HUMAN-) in Waterford (Waterford = An Déise = DE-ISE) (DEHUMANISE),
14 Hard to please (PICKY) detective (PI-) going to Cork (-C-) and Kerry (-KY) (PICKY),
16 He (HE = Helium = NOBLE GAS) is not moving (INERT) – how amusing is that? (GAS) (INERT GAS),
17 Unlimited number (INFINITY) misidentifying missing midges (‘misidentifying’ missing ‘midges’ = intifyin = INFINITY),
19 Mother (-MA-) taken in by visitor to Oz (Toto = TO-TO) (TOMATO) offering fruit (TOMATO),
21 Strange (= anagram indicator) role – it (role it = LOITER) is what you’d expect a lounge lizard to do (LOITER),
23 Outlet (SHOP) for posh (posh) model (= anagram indicator) (posh = SHOP),
24 Celebrity dismisses Rebel (‘celebrity’ dismisses ‘rebel’ = city = CITY) Cork (CITY).