BOBCAT kicks off the week…
A nice challenge from this setter. The feline Nina actually helped with a couple of clues once I spotted it. Plenty of clues stood out, but I particularly liked 20a.
Thanks BOBCAT!

ACROSS
1. Oppose indigenous Australian changing leader (6)
COMBAT
WOMBAT (indigenous Australian, changing leader)
4. Old campaigner, regularly AWOL, oddly succeeded with retrospective appeals (8)
ODYSSEUS
[aw]O[l o]D[dl]Y (regularly) + S (succeeded) with (SUES)< (appeals, <retrospective)
10. Escape from Arab’s condemnation (7)
ABSCOND
[ar]ABS COND[emnation] (from)
11. I’m obsessed with missing streetwalker, as street’s evacuated (7)
STALKER
S[tree]T[w]ALKER (W (with) missing, as STREET's evacuated (i.e. remove the TREE))
12. At least a fortnight reeling, unfocused and awry (4)
SKEW
(WE[e]KS (at least a fortnight))< (<reeling, unfocused)
13. Reform inject millions into development of beers and ales (10)
REASSEMBLE
M (millions) into (BEERS and ALES)* (*development of)
16. Match 50% of upturn in French company (3,3)
CUP TIE
UPT[urn] (50% of) in CIE (French company, equivalent to Co.)
17. Public set to embrace New Age (7)
GENERAL
GEL (set) to embrace (N (new) + ERA (age))
20. Potentially hot stuff in Macbeth’s introduction? (7)
METHANE
ME THANE (Macbeth's introduction?)
21. Thanks given to about two-thirds of top performing military (6)
TATTOO
TA (thanks) given (TO about TO[p] (two thirds of))
24. One almost passed on, desperately killing time (4,6)
OPEN SEASON
(ONE + PASSE[d] (almost) + ON)* (*desperately)
25. Land that’s surrounded by small lake — or the opposite? (4)
ISLE
IE (that's) surrounded by (S (small) + L (lake)) – or the opposite
27. Disqualify ruler such as George III? (7)
BARKING
BAR (disqualify) + KING (ruler)
29. Legendary power base cased by PI (4,3)
EVIL EYE
VILE (base) cased by EYE (PI, Private Investigator)
30. Decline to go off after fellow pinching wife (8)
DOWNTURN
TURN (go off) after (DON (fellow) pinching W (wife))
31. Secret place to sleep could be remote (6)
KEYPAD
KEY (secret) + PAD (place to sleep)
DOWN
1. Outstanding performer in school play? (5,3)
CLASS ACT
2. Superb work of, perhaps, King and Queen? (11)
MASTERPIECE
MASTER (king) + PIECE (queen?)
3. Scrap involving a queen’s consort? (4)
ATOM
A + TOM (queen's consort, cat)
5. Outcome where officer leading special forces starts to take extreme risks? (8)
DISASTER
DI (officer) leading SAS (special forces) + T[ake] E[treme] R[isks] (starts to)
6. Pet eats mice as directed (7,3)
SIAMESE CAT
(EATS MICE AS)* (*directed)
7. Church brass declines, I’m afraid (3)
EEK
[ch]EEK (brass, declines CH (church))
8. Test the suitability of North American tin cans (6)
SCREEN
CREE (North American), SN (tin) cans
9. I’m going to pass on gold stocks (5)
ADIEU
DIE (to pass on), AU (gold) stocks
14. It’s said to make kippers more appealing (6,5)
BEAUTY SLEEP
15. Thing made by this working group? (5,5)
NIGHT SHIFT
THING being an anagram (shift) of NIGHT
18. Threaten to pacify? (8)
ENDANGER
19. Idiot earl and countess possibly upset by the Crown (8)
BONEHEAD
(E (earl) + NOB (countess, possibly))< (<upset) by HEAD (crown)
22. Ban rector and bishop implicated by old ministry papers (6)
FORBID
(R (rector) and B (bishop)) implicated by (FO (old ministry) + ID (papers))
23. Sort of dog that gets into fights (5)
BOXER
26. Help attacker to vanquish resistance on all sides (4)
AIDE
[r]AIDE[r] (attacker, to vanquish R (resistance) on all sides)
28. Naked hostility exhibited in review (3)
RAW
(WAR)< (hostility, <exhibited in review)
Great fun. Not easy, but doable, just as I like it.
Didn’t see ‘unfocused’ = ‘removing the centre’ so couldn’t parse SKEW even though I could see ‘weeks’ was involved.
Thanks Bobcat and Teacow.
In 4ac I took AWOL to mean missing, hence o[d]d[l]y + etc, but either way …
Yes, good chewy puzzle, thanks Bobcat and Teacow.
Yes quite chewy but got there in time. Quite a few lightbulb moments required, and for once the Nina gave me a couple of letters which were a big help. Liked methane, barking, Siamese cat.
I thought Odysseus was just every other letter (ie regularly AWOL) from OdDlY then per the blog, and I thought class act was a double defn.
Thx both
For the first time with this setter I spotted the Nina which helped me with 19d BONEHEAD. I agree with Sourdough’s assessment of the puzzle.
Thanks Bobcat and Teacow.
Thanks Bobcat and Teacow
4ac: When solving, I parsed this the same way as suggested in comments 2 and 3. However, in my view, there is no good reason why “regularly” should not mean every third letter from a sequence, and Teacow’s parsing explains the specific choice of AWOL in the clue.
Thanks Bobcat for a top-notch crossword. Plenty of favourites including ABSCOND, GENERAL, ATOM (a cat clue), SIAMESE CAT (great surface & another cat clue), ADIEU, NIGHT SHIFT, ENDANGER, & the Nina, TIGER CUB. I revealed KEY PAD & SKEW and I never could figure out the Byzantine parsing of the latter. Thanks Teacow for the blog.