Across:
1 Splinter groups disregard stronger (‘splinter groups’ disregard ‘stronger’ = pliups = PUPILS) members of a certain class (PUPILS),
4 Mighty (SMASHING) craic (“craic” = “crack” = SMASH-) overheard (= homophone indicator) in (-IN-) Government (-G) (SMASHING),
9 The prickly types (THORNS) in North’s (norths = THORNS) Order (= anagram indicator),
10 One comic (one comic = ECONOMIC) misprint (= anagram indicator) relates to the fiscal space (ECONOMIC),
12 Tradition (LOR-E) about golf (-G-), what’s required in fishing (-NET-) and extreme tennis (extreme ‘tennis’ = -T) (LORGNETTE) makes the dramatic action clearer (opera glasses = LORGNETTE),
13 Include autodidact, originally (include ‘autodidact originally’ = ACTOR) a man of many parts (ACTOR),
14 Organisation (UN-) is not despotic (-DEMOCRATIC) (UNDEMOCRATIC) or totalitarian (UNDEMOCRATIC),
18 Graduate (BA-) is on the board (-KING on chess board) with prisoner-of-war (POW-) and the German (the = -DER) (BAKING POWDER) agent responsible for The Rising (BAKING POWDER),
21 It’s a sign (ARROW) of what’s raw or (raw or = ARROW) off (= anagram indicator),
22 Paper (TELEGRAPH) in the post (TELEGRAPH post),
24 Minister (CLERIC-) gets a (-A-) tip for lots (tip for ‘lots’ = -L) (CLERICAL) of office work (CLERICAL),
25 Firm (CO-) structure on the shore (-PIER) (COPIER) is the work of the forger (COPIER),
26 Comes before (PRECEDES) postscript (P-S) about troublesome (= anagram indicator) decree (decree = -RECEDE-) (PRECEDES),
27 Position (STATUS) limits state apparatus (limits ‘state apparatus’ = STATUS).
Down:
1 Picks up (= reversal indicator) bug (bug = tap = PAT-) at university (University of Limerick = -UL-) near Oxford (-O-) from you and me (-US) (PATULOUS) and it’s spreading through the various branches (PATULOUS),
2 Stick up (PROTRUDE) for boisterous (= anagram indicator) red-top (red top = PROT-DE) covering Russia (-RU-) (PROTRUDE),
3 Some individual in England (some ‘individual in England’ = LINEN) is hung out to dry (LINEN),
5 Really famous artist (MICHELANGELO) from Band Aid (MIC-) got endless (p) help (‘help’ without ‘p’ = -HEL-) in Genoa (Genoa = -ANGE-O) playing (= anagram indicator) around port (port/left = -L-) (MICHELANGELO),
6 Is it fair (half of) of Sandra (half of ‘Sandra’ = SAN) joining Dublin Waltz (MARINO Waltz) (SAN MARINO) production in old European capital? (SAN MARINO),
7 Meat in (meat in = INMATE) stew (= anagram indicator) could be from an American can locally? (from American “can” / jail = INMATE),
8 Great (G-) actor (actor = -O-CART) playing (= anagram indicator) (GO-CART) in one of those vehicles for children (GO-CART),
11 Basic equipment always needed (STOCK -IN-TRADE) for The Animals’ (STOCK-) single (I-) and opening notes (opening ‘notes’ = -N) by Traffic (-TRADE) (STOCK-IN-TRADE),
15 Main wheel (main wheel = MEANWHILE) burst (= anagram indicator) at the same time (MEANWHILE),
16 Best possible (IDEAL-) result from university (1ST = -IST) (IDEALIST) for visionary (IDEALIST),
17 Old (O-) church member (Roman Catholic = -RC-) is strict (-HARD-) on self-starter (‘self’ starter = -S) (ORCHARDS) and those with the plum jobs perhaps (ORCHARDS),
19 Crazy (MADCAP) head of the Family (MA-) Department (-D-) from Cork (cork = -CAP) (MADCAP),
20 Little bit of blow (BREEZE) for a walk in the park (is easy/ is a BREEZE),
23 Gets light ointment applied to heads (‘gets light ointment applied to’ heads = GLOAT) – rub it in (GLOAT).