Not quite DA's usual precision, but fairly tricky as usual. Some fun clues but I didn't really find it that enjoyable.

Across

4

Stellar warrior captain cut supporter on the ear (9)
CHEWBACCA — C (captain) HEW (cup) homophone of BACKER (supporter)

9

(& 28-across) Drunk racing at sea? (5,6,2,3,4)
THREE SHEETS TO THE WIND — cryptic def.

10

Cabinet hosting ASEAN leaders for tea (3)
CHA — first letters of Cabinet Hosting Asean

11

A third of piglets with siblings to shine? (7)
GLITTER — G (third letter of piglets) LITTER (siblings)

12

Pronounced billionaire author as 9- 28-across (7)
ROLLING — homophone of ROWLING (billionaire)

13

Waiting about hospital to visit senior (2,4)
ON HOLD — ON (about) H (hospital) OLD (senior)

17

Serious complaint quietly poleaxed French solver? (8)
GRIEVOUS — GRIpE (complaint) without (poleaxed) p (quietly), VOUS (French solver; you)

19

Pool worker once loading dirty pistol (6)
TYPIST — hidden (loading) in dirTY PISTol

22

Half of continent borders country reflecting charm (7)
ENAMOUR — EURope (half of continent) outside (borders) reversal (reflecting) of OMAN (country)

23

(& 6-down) Engineers dub such Kylie solo? (1,6,2,2,5)
I SHOULD BE SO LUCKY — anagram (engineers) of DUB SUCH KYLIE SOLO, &lit

25

Rascal to spike missing beer (3)
IMP — IMPale (spike) without ale (beer)

26

Peaceful Canberra protest rubbished by statesmen (4,7)
TENT EMBASSY — anagram (rubbished) of BY STATESMEN

29

Semi exchanged first consignment for new chest (5)
TRUNK — TRUcK (semi) with c (first letter of consigment) -> N (new)

Down

1

Spring sound (3)
FIT — double def.

2

Sizeable banks to lavish macro-gains occasionally deposited (7)
LARGISH — LH (outside letters of lavish) outside (deposited) ARGIS (even letters of macro-gains)

3

Cleaned up benches blocking way (5)
SWEPT — reversal (up) of PEW (benches) inside (blocking) ST (way)

4

Novel co-author losing gold band (6)
COHORT — anagram (novel) of CO-auTHOR without au (gold)

5

Viewer’s solution for Spooner’s sober manoeuvres? (8)
EYEDROPS — Spoonerism of DRY (sober) OPS (manoeuvres)

7

Brasher spaniel bites basenji’s tail (7)
COCKIER — COCKER (spaniel) outside I (last letter of basenji)

8

Joined a good priest aspiring to get married (11)
AMALGAMATED — reversal (aspiring) of A G (good) LAMA (priest), MATED (married)

11

Novelist gave tips on love, perhaps, reflected in retired worker (6,5)
GEORGE ELIOT — GE (outside letters of gave) O (love), reversal (reflected) of EG (perhaps) in reversal (retired) of TOILER (worker)

14

(& 15-across) ABC series following dates, orange? (4,2,3,8)
LOVE ON THE SPECTRUM — LOVE (dates) ON THE SPECTRUM (orange)

16

Drink off-limits in pound near one Liverpool Plains town (8)
QUIRINDI — RIN (drink without outside letters) inside QUID (pound) I (one)

18

Cornered snake awash in lead-free wine (2,1,4)
IN A SPOT — ASP (snake) inside pINOT (wine without first letter)

20

(& 1-across) Twice USA fills middle of Niagara, ruining majestic water feature (7,5)
IGUASSU FALLS — anagram (ruining) of USA USA FILLS G (middle letter of niagara)

21

Irish girl taped part of leg support? (6)
SINEAD — homophone (taped) of SHIN (part of leg) AID (support)

24

Dress horse? Partly (5)
HABIT — H (horse) A BIT (partly)

27

Back to quantify British gross! (3)
YUK — Y (last letter of quantify) UK (British)