Across:
8 Each (each = CHA-E) criminal (= anagram indicator) sheltering heartless (u) Persian (‘rug’ without ‘u’ = -RG-) (CHARGE) from The Bill (CHARGE),
9 Is eager to get things done quickly (IN A HURRY) for popular (IN) academy (A) near Rush (rush = HURRY) (IN A HURRY),
10 A measure of one of those grounded types (ACRE) of sources coming off racecourses (‘sources’ coming off ‘racecourses’ = race = ACRE),
11 It’s a lesson for the Irish (TEACH CLASS) offering to run a finishing school presumably (TEACH CLASS),
12 Tests (HAS A GO) with tries? (HAS A GO),
14 Agent (rep) is not finished (p) (‘rep’ without ‘p’ = RE-) with the people (-PUBLIC) (REPUBLIC) on this island (REPUBLIC),
15 Awful (= anagram indicator) cheaters (cheaters = TEACHERS) from Dean’s Place (dean’s place = COLLEGE) (TEACHERS COLLEGE) training those who want to do the jobs in 11 and 22 across (TEACHERS COLLEGE training those to ‘teach class’ and ‘teach maths’),
18 Endless (h) ready money (‘cash’ without ‘h’ = CAS-) for the footwear (-SOCKS) (CASSOCKS) designed by the costume department at The Abbey presumably (CASSOCKS),
20 Class fools (CLOWNS) from college (C-) dispirited (-LOW-) by national school (-NS) (CLOWNS),
22 Familiarise someone with the figures (TEACH MATHS) opening 11 across (opening ‘teach class’ = TEACH) for one of the subjects (MATHS) (TEACH MATHS),
24 It’s fairly harmless (TAME) what’s in the First Amendment (what’s in the ‘First Amendment’ = TAME).
25 It’s not easy (it’s HARD-) to bet against (-BACK) (HARDBACK) what the bookmaker is supporting (HARDBACK),
26 Having the knowledge (know one’s ONIONS) of edible bulbs (ONIONS).
Down:
1 Two Trim (p + p) lads (‘chap + chap’ both without ‘p’ = CHA-CHA) from Latin American movement (CHA-CHA),
2 Life peer loses pile (‘life peer’ loses ‘pile’ = feer = FREE) that’s unoccupied (FREE),
3 Seth (Seth = -EST H-) cracking up (= anagram indicator) in Italian city (R-OME) (REST HOME) looking after the old folks (REST HOME),
4 Knocks back (= reversal indicator) a (-A) mouthful of drink (sip = PIS-) (PISA) in Italian city (PISA),
5 White (W-) Snake (asp = -AS- -P) get to grips with most of (m) the buzz (‘hum’ without ‘m’= -H U-) (WASH UP) to get clean? (WASH UP),
6 Shell (shell/case = HULL-) has a (-A-) test site (lab) around (= reversal indicator) (lab = -BAL-) Oxford (-O-), Ring (-O) (HULLABALOO) and Donnybrook (donnybrook/scene of uproar = HULLABALOO),
7 In need of immediate attention (PRESSING) working in a job developing the port, for example (PRESSING the grapes),
13 Security are aware of this (ACCESS CODE) approach (ACCESS) and delivery method (cash on delivery = COD-) for drugs (-E) (ACCESS CODE),
14 Losing the head (c) at critical points (‘crises’ without ‘c’ = RISES) in stands (RISES),
16 Dave (Dave) retires (= reversal indicator) (Dave = EVAD-) at end of surveillance (end of ‘surveillance’ = -E-) duty (TAX) (EVADE TAX) to work in the black economy (EVADE TAX),
17 Old (O-) conservative (-C-) Shakespearean character (Casio in Othello = -CASIO-) gets to start at new (start at ‘new’ = -N) (OCCASION) event (OCCASION),
19 Take a couple of breaths in the passage (punctuation marks in passage/book = COMMAS) – it could be the butterflies? (butterflies = COMMAS),
21 Identifying (NAMING) leading man ignoring deal (“leading man” ignoring “deal” = ingman = NAMING),
23 Ice skater cries out (‘ice skater’ ‘cries’ out/without ‘cries’ = kate = TAKE) in bit of filming (TAKE),
24 Stumble (TRIP) around troop ship (around ‘troop ship’ = TRIP).