Thanks to Slormgorm, perhaps more restrained here than when he sets under another pseudonym. Definitions are underlined in the clues.
Across
1 Pine for one tender to court daughter (8)
SOFTWOOD : SOFT(gentle;tender) plus(to) WOO(to court;to seek the favour of someone) + D(abbrev. for “daughter”).
Defn: The wood from, for example;for one, the pine tree.
5 Extend study on Soviet Politburo leaders (6)
SPREAD : READ(to study a specific subject at university) placed after(on) 1st letters, respectively, of(… leaders) “Soviet Politburo“.
10 Woman granny cannibalised (reportedly) (7)
NANETTE : NAN(term for one’s grandmother;granny) + homophone of(… (reportedly)) “ate”(consumed;cannibalised).
11 Follow the rules of conservative in fine fettle (7)
CONFORM : C (abbrev. for a Conservative, member of the Conservative Party) + [ ON FORM ](in fine fettle;performing well).
12 May one go out with enthralling Dutch runner (9)
CANDIDATE : [CAN I DATE](can;may I;one date;go out with somebody, especially when courting) containing(enthralling) D(abbrev. for “Dutch”).
Defn: One who runs;stands for election.
13 Crime that makes clergyman lose head (5)
ARSON : “parson”(a clergyman) minus its 1st letter(lose head).
15 Cad with Irish accent’s not British (5)
ROGUE : “brogue”(a marked Irish accent when speaking English) minus(…’s not;has not) “B”(abbrev. for “British”).
16 Lively article one friend finally read (8)
ANIMATED : AN(an article in grammar) + I(Roman numeral for “one”) + MATE(a friend) + last letter of(finally) “read“.
19 Breaking up can be wonderful (8)
SMASHING : Double defn: 2nd: Slang for “wonderful!”;excellent!
20 Possibly unhappy about wind-up (3,2)
PUT ON : Reversal of(… about) [NOT UP](feeling down;unhappy).
Defn: A deception;an attempt to make someone believe something that is false.
The nounal answer should perhaps be hyphenated, as the definition is.
21 Dance music record by Orbital originally (5)
DISCO : DISC(a format for reproducing a recording) plus(by) 1st letter of(… originally) “Orbital“. The latter is an English electronic dance music duo.
23 Synopses of a bishop’s religious treaties (9)
ABSTRACTS : A + B(abbrev. for “bishop” in chess notation) + TRACTS(religious pamphlets;treatises). There’s a typo in the clue’s last word.
25 Might one create a ring of cattle? (7)
COWBELL : Cryptic defn: An article worn around a cow’s neck which might give a ringing sound.
27 Trained doctor meeting unwell editor (7)
DRILLED : DR(abbrev. for “doctor”) plus(meeting) ILL(unwell;sick) + ED(abbrev. for “editor”).
28 Kid singer with wig on head (3,3)
RUG RAT : RAT(a singer;an informer) placed after(with … on head) RUG(slang for a wig).
Defn: A child not old enough for school.
29 Captured renegade ran sneakily around cages (8)
ENSNARED : Reversal of(… around) and hidden in(… cages) “renegade ran sneakily“.
Down
1 Cushy job initially selling popular drug remedy (8)
SINECURE : 1st letter of(initially) “selling” + IN(popular;in fashion) + E(abbrev. for the drug, Ecstasy) + CURE(a remedy).
2 Manage funds differently for entertainments (3,3,5)
FUN AND GAMES : Anagram of(… differently) MANAGE FUNDS.
3 One who sees over time one’s clever humour (9)
WITTINESS: WITNESS(one who sees) containing(over) [ T(abbrev. for “time”) + I(Roman numeral for “one”) ].
4 High-brow musical work the Queen admires primarily (5)
OPERA : OP(abbrev. for “opus”, a musical or literary piece of work) + ER(abbrev. for “Elizabeth Regina”, the Queen) + 1st letter of(… primarily) “admires“.
6 Rubbish lawyer, one with two black eyes? (5)
PANDA : PAN(to rubbish;to criticise severely) + DA(abbrev. for “District Attorney”, in the US, a lawyer).

7 I shot subordinate of ensign at the front (3)
EGO : GO(a shot;an attempt, as in “have a go at it”) placed below(subordinate of;inferior to, in a down clue) 1st letter of(… at the front) “ensign“.
Defn: One’s self;one’s sense of identity.
8 Fellow describing flipping yours truly as a fiend (5)
DEMON : DON(a fellow;a lecturer in a university) containing(describing) reversal of(flipping) ME(yours truly;the one who’s writing/speaking).
9 Crafty GM in chess Short annoyed (8)
SCHEMING : Anagram of(… annoyed) [ GM IN + “chess” minus its last letter(Short) ]. And Nigel Short is an English chess GM (grandmaster) himself.
14 Acts clear up after tumbling in this? (11)
SPECTACULAR : Anagram of(… after tumbling) ACTS CLEAR UP.
Defn: A performance consisting of spectacular acts.
A WIWD (wordplay intertwined with definition) clue.
16 Friendly catholic absorbed by self-doubting question? (8)
AMICABLE : C(abbrev. for “Catholic”) contained in(absorbed by) [ AM I ABLE? ](a question expressing doubt about one’s own ability).
17 When individual internalises one malicious remark (9)
ASPERSION : AS(when, as in “as you enter the door”) + PERSON(an individual) containing(internalises) I(Roman numeral for “one”).
18 Unbalanced? Indeed so, having to whirl about! (3-5)
ONE-SIDED : Anagram of(…, having to whirl about) INDEED SO.
21 Dean’s half-finished my interior design (5)
DECOR : “Dean” minus its last 2 letters(…’s half-finished) + COR!(like “my!”, an expression of surprise).
22 Old and wicked Greek character (5)
OMEGA : O(abbrev. for “old”) + MEGA(like “wicked”, slang for “excellent”).
24 Bit of a lather heading to any northern country (5)
SUDAN : SUD(a bit of;singular of suds;bubbles;lather, as in its derivative “soapsud”) + 1st letters, respectively, of(heading to) “any northern“.
26 You might say Victoria Beckham is comic (3)
WAG : WAG(the wife or girlfriend of a sportsman, from the acronym for Wives And Girlfriends, characterised by a high media profile. You might say that Mrs. David Beckham is one).
Defn: A joker.
Thanks to Stormgorm and scchua. I got WAG thanks to a recent Guardian puzzle that used the term but was delayed by starting with “assertion” (which doesn’t parse) instead of ASPERSION. I took a while before spotting I=EGO and took even longer before seeing the reversal for ENSNARED. All in all, a challenge for me that I much enjoyed.
I’m afraid that I can’t follow sccua’s parsings at all, and especially in the explanation of ENSNARED. If a kind soul would translate the parsing into a standard format, I’d be most grateful.
Bob Sharkey @2
ENSNARED is a hidden reversal in ‘renegaDE RAN SNEakily’. The reversal indicator is ‘around’ and the inclusion indicator is ‘cages’.
Thanks Gaufrid. Didn’t spot it. I usually underline hidden answers, myself, with the explanation ‘hidden’. Less room for confusion.
Thanks Slormgorm and schhua
An interesting puzzle that wasn’t all that hard but it had some clues with quite a bit of substance to them. In 10a, I had heard of people using the word ‘et’ to mean ate, but didn’t realise that it was regarded as a homophone of it – there does seem to be some different thoughts on it too – https://en.wiktionary.org/wiki/Talk:et
Didn’t properly parse a couple – didn’t see RAT = singer in the informer sense at 28a and didn’t properly get my head around what was going on with PUT ON. They were my last couple in.