Was 'winded' googling and reading the long winded clues.
ACROSS
8 Gratify Henry’s ilk no end leaving to fool around (6) PANDER Anno pending (Addendum - P(-h)(-ilk)ANDER - See comments)
9 European politician’s allegiances; commitments basically are most
hollow (8) EMPTIEST {E}{MP}{TIES}{commiTments}
10 Highway 78 perhaps missed out marker (8) MILEPOST {MI}LEPOST Anno pending (Addendum - {MI}{L{EP}OST} - See comments)
12 Blonde frayed at the edges, with silver lining; sign of
seniority (3,3) OLD AGE {gOLD {AG}En}
13 Resurgences of servitude binding one vassal, beginning to
return, as year ends (8) REVIVALS {yRE{VI}VALS}<= Not sure of Anno See comments
15 Ridicule report about garment and casual wear (1-6) T-SHIRTS {T-{SHIRT}S}(~tease) I thought ridicule report would be 'tsk', rom tsk-tsk? See coments
17 We declined carnation from a girl, back in USA (7) FLORIDA {FLOweR}{IDA}
20 New independent national character, for instance, reflected in
African (8) NIGERIAN {N}{I}{GE<=}{RIAN<=} (Addendum - {N}{I}[{GE}{RIA}{N}<=] - See comments)
22 Mammal in Manila harassed (6) ANIMAL*
23 A road crossing short alley at an angle (6) ASLANT {A}{S{LANe}T}
25 Opera scripts in book, strangely written, without covers (8) LIBRETTI {LIB}{wRITTEn}* Lib from Library? Then it should have been books.
26 Poisonous plants perhaps brought about the end of Socrates?
(8) HEMLOCKS [GK]
27 Clears peculiar looking membrane around the eyes (6) SCLERA*
DOWN
1 Exceptionally prepared sir, and — voila — see pasta dishes!
(8) RAVIOLIS {SIR+VOILA}*
2 Ground stroke featuring Nadal, in the centre, raises excitement
levels (10) ADRENALINE {NADAL+IN+REE?}* ?(Addendum - {A{naDal)RENA}{LINE} - See comments)
3 Hollow in wood? Nothing in it! (6) GROOVE {GRO{O}VE}
4 Ultimately length etc., perhaps a measure, couple finally needed,
for unit of area (7) HECTARE {H}{ETC*}{A}{measuRE}
5 Turmoil in Indian state; unending happiness cut short by gangster
(8) UPHEAVAL {UP}{HEAVen}{AL} Unending and then cut short to remove two letters?
6 Court order with conditional decree, carried by Tunisian (4) NISI [T]
7 Mule revolts, beset by pain and torture (6) ASSAIL {A{SSA<=}IL}
14 Chop removing core and fillet basically into say extremely, long
strands of pasta (10) VERMICELLI VERMIC{tELLIf} Anno pending (Addendum - {VER{MInCE}{fiLLet}I}(~very) - See comments)
16 Three panelled artwork showing travel by Greek goddess of fortune, briefly (8) TRIPTYCH {TRIP}{TYCHe}
18 People using drawing boards are mainly designers of roof
supports (8) DRAFTERS {D}{RAFTERS}
19 Girl’s report announces agenda for expert maybe (7) ANALYST (~anna}{ANA}{LYST}(~list)
21 Rhythmic march on foot (6) INSTEP {IN}{STEP}
22 Is she superior born, to be protected by President’s security
service? (6) ABBESS {A{B}BE}{SS} Why 'Is she'?
24 Jack, the French expert (4) ABLE {AB}{LE}