ACROSS

1 Test one canonised in meeting (5) 
TRYST - meeting (def) from TRY (Test) ST (one canonised)

4 City preserves, it's said, chopped grub (8) 
SALZBURG - City (def) from SALTZ (homophone (it's said) of SALTS=preserves) and BURG anagram (chopped) of GRUB
 
8 Biased enquiry burdened one working after mission (7,7) 
LOADED QUESTION  - Biased enquiry (def) from LOADED (burdened) I (one) ON (working) after QUEST (mission)

10 Cleaner fuel disfigured lean dude (8) 
UNLEADED  - Cleaner fuel (def) from anagram (disfigured) of LEAN DUDE

11 Arch in plain reportedly (6) 
INSTEP  - Arch (def) from IN STEP (homophone (reportedly) of STEP(PE) (plain)

12 Fix unpleasant people's punctures (3-6) 
PIN-PRICKS  - punctures (def) from PIN (Fix) PRICKS (unpleasant people)

15 Crouch and frighten monarch (5) 
COWER  - Crouch (def) from COW (frighten) ER (monarch)

17 Destruction of note after cutback (5) 
WASTE  - Destruction (def) from TE (note)  after WAS (cut=SAW back)

18 Horses almost hold up rugby team (9) 
STALLIONS  - Horses (def) from STAL (almost STALL=hold up) LIONS (rugby team)

19 Look at permit for aperture(6) 
EYELET  - aperture (def) from EYE (look at) LET (permit) 

21 How mince is prepared for dish (4,4) 
CHOW MEIN - dish (def) from anagram (is prepared) of HOW MINCE

24 How one overpays in Bullring location (7,3,4) 
THROUGH THE NOSE - How one overpays (def) (cryptic def) A bull's ring is placed through the nose

25 Former court expert ready with ink at first for scrawls on walls (8) 
GRAFFITI  - scrawls on walls (def) from GRAF (Former court expert Steffi Graf) FIT (ready) with I (ink at first)

26 Produces publication for educators about Hubble returning (5) 
TEEMS - Produces (def) from TES (Times Educational Supplement) about EM (Hubble=ME returning)

DOWN

1 Cosmetic dust director with ace and low trump dispersed (6,6) 
TALCUM POWDER  - Cosmetic dust (def) from anagram (dispersed) of D (director) with ACE and LOW TRUMP

2 Young animals angry with lies circulated (9) 
YEARLINGS  - Young animals (def) from anagram (circulated) of ANGRY with LIES

3 Character essential to Homer cited by Riley-Smith et al (5) 
THETA  - Character essential to Homer (def) contained in (cited by) Riley-SmiTH ET Al

4 Tory abandoning results ordered series (9) 
SEQUENCES  - ordered series (def) from (CON)SEQUENCES (Tory abandoning results)

5 Emblem in The Valleys revealed orally by confidence breaker (4) 
LEEK - Emblem in The Valleys (def) from homophone (revealed orally by) LEAK (confidence breaker)

6 A bat Colin breaks on plants (9) 
BOTANICAL  - on plants (def) from anagram (breaks) of A BAT COLIN

7 Rest of Australian natives at junction (5) 
ROOST  - Rest (def) from ROOS (Australian natives) at T (junction)

9 Vocalists in Aida, say, with burners? (5-7) 
OPERA-SINGERS  - Vocalists (def) from OPERA (Aida, say) with SINGERS (burners?)

13 Recited readily about European taken away (6,3) 
REELED OFF - Recited readily (def) from RE (about) E (European) LED OFF (taken away)

14 Food pigs with 3 digested (9) 
SPAGHETTI  - Food (def) from anagram (digested) of PIGS and THETA (answer to 3)

16 Complete selection is healthy (9) 
WHOLESOME  - healthy (def) from WHOLE (Complete) SOME (selection)

20 Old number, one the rapper covered (5) 
ETHER  - Old number (anaesthetic) (def) contained in (covered) onE THE Rapper

22 Remainder heard to twist violently (5) 
WREST  - (def) from 

23 Fruit sounding unattractive (4) 
UGLI  - Fruit (def) from homophone (sounding) of UGLY (unattractive)