Across:
8 Editorials dismiss diet (‘editorials’ dismiss ‘diet’ = orials = SAILOR) with salt (salt/old salt = SAILOR),
9 Endorse a (endorse a = REASONED) play (= anagram indicator) that’s well presented (REASONED),
10 Mysterious (= anagram indicator) duo (duo = -UDO) (JUDO) after (= positional indicator) justice (J-) for those defending themselves in Osaka (JUDO),
11 Kind of sweet (GOBSTOPPER) for Marsh (marsh/bog = GOB-) retiring (= reversal indicator) to Cork (cork = -STOPPER) (GOBSTOPPER),
12 Madeleine dismisses lie (‘Madeleine’ dismisses ‘lie’ = madene = DEMEAN) as put down (DEMEAN),
14 Music (ROCK music) similar to 8 across (SALT similar to ‘sailor’) (ROCK SALT) coming out of The Cellar (ROCK SALT from the salt cellar),
15 Peacekeeper (United Nations = UN-) on diet (diet/assembly = -PARLIAMENT) cooked (= anagram indicator) ray (ray = -ARY) (UNPARLIAMENTARY) contrary to house rules (UNPARLIAMENTARY),
18 Is it meat (is it meat = IMITATES), bananas (= anagram indicator) or parrots? (IMITATES),
20 Ruffle someone’s feathers (ENRAGE) with a Green (a green = ENRAGE) remedy (= anagram indicator),
22 Half the bunch of flowers (half the ‘posy’ = -SY-) cut into pieces (-CHOP-) in trail (P-ATH) (PSYCHOPATH) recognised by profiler (PSYCHOPATH),
24 No Kir in milk bar (no ‘Kir’ in ‘milk bar’ = mlba = LAMB) for one of Mary’s followers (LAMB),
25 Weekend (‘week’ end = -K-) in Chester (Chester = S-ETCHER) mobile? (= anagram indicator) (SKETCHER) One can draw one’s own conclusions! (SKETCHER),
26 Hesitantly drops this (‘hesitantly’ drops ‘this’ = eantly = NEATLY) in an orderly fashion (NEATLY).
Down:
1 Partner (MAT-E) admits old city (-UR-) (MATURE) is developed as much as it can be (MATURE),
2 In addition (ALSO) to some potential soundtrack (some ‘potential soundtrack’= ALSO),
3 Gloria in (Gloria in = ORIGINAL) dress? (= anagram indicator) That’s a first! (ORIGINAL),
4 Pub (bar = -RAB) chain to open (chain to open = C-) up (= reversal indicator) (CRAB) – is that a sign? (CRAB is sign of Cancer),
5 Architect releases her (‘architect’ releases ‘her’ = acitct = TACTIC) plan (TACTIC),
6 One (-I-) is consumed by pile in the farmyard (COMPOS-T-) – initial odour (initial ‘odour’ = -O-) is never-ending (‘never’ ending = -R) (COMPOSITOR) and affects what’s going on in printworks (COMPOSITOR),
7 Religious type (JEW-) takes head off (t) bank employer (‘teller’ without ‘t’ = -ELLER) (JEWELLER) for casting the first stone perhaps (JEWELLER),
13 The Spanish (the = EL-) sparking wine (-ASTI-) from Barcelona, for instance (-CITY), (ELASTICITY) is good at a stretch (ELASTICITY),
14 Goes through the books (READS) of Great Dane’s missing agent (‘Great Danes’ missing ‘agent’ = rdaes = READS),
16 Drunk in Tokyo (-SAKE) goes after (= positional indicator) big shot (NAME-) (NAMESAKE) – it’s a similar brand my father gave me (NAMESAKE),
17 Show off (= anagram indicator) the plane (the plane = ELEPHANT) – it’s a Jumbo (jumbo = ELEPHANT),
19 Knocks back (= reversal indicator) drink (port = TROP-) – it’s a reserved type (shy) that needs no introduction (s) (‘shy’ without ‘s’ = -HY) (TROPHY) in The Laurels? (laurels/prize = TROPHY),
21 Run a risk (GAMBLE) with a feature of the roof (GA-BLE) around back of the stadium (back of ‘stadium’ = -M-) (GAMBLE),
23 A measure of one of those grounded types (ACRE) of sources coming off racecourses (‘sources’ coming off ‘racecourses’ = race = ACRE),
24 Charge (LOAD) one of those stable types (stable lad = L-AD) admitting nothing (-O-) (LOAD).