PHSSTHPOK's third outing this year (I believe)…
I've enjoyed the previous Monday offerings from this setter, and this was no exception.
I must admit I'd never heard of the pig in 22a, but there weren't too many possibilities given the anagram fodder. 9a was my LOI, and ended up as one of my favourites, along with 13a and 4d,
Thanks PHSSTHPOK!

ACROSS
1. Robert bumps off articulated vehicles in the snow (10)
BOBSLEIGHS
BOB (Robert) "slays" (bumps off, "articulated")
7. Except the foot, wax part of leg (4)
SHIN
SHIN[e] (wax, except the foot)
9. Insulator for first piece of audio equipment? (4)
MICA
MIC A (first piece of audio equipment, followed by MIC (microphone) B)
10. Run through by musician: it’s sharp (5,5)
BOWIE KNIFE
KNIFE (run through) by BOWIE (musician, the late, great, David Bowie)
11. Army captures Nebraska plain (6)
HONEST
HOST (army) captures NE (Nebraska)
12. “Sound as a bell!” put in elderly female relative, with a sneer (8)
TAUNTING
TING (sound as a bell), put in AUNT (elderly female relative)
13. Grave robber’s leading two characters to head covering (8)
SOMBRERO
SOMBRE (grave) + RO[bbers] (leading two characters)
15. Stone axes have no back (4)
ONYX
(X Y (axes) have NO)< (<back)
17. Shot some pellets exploding duck heads (4)
SPED
S[ome] P[ellets] E[xploding] D[uck] (heads)
19. Crazy to go round this small danger when diving (3,5)
THE BENDS
THE BEND (crazy to go round this, go round the bend) + S (small)
22. Rabbi cooked us a pig (8)
BABIRUSA
(RABBI)* (*cooked) + US + A
23. Diet society meet in pubs (6)
LOCALS
LO-CAL (diet) + S (society)
25. Plan for teacher to look after child (10)
MASTERMIND
MASTER (teacher) + MIND (look after child)
26. What was once worn to Georgia (4)
TOGA
27. President loses heart to Spanish labourer (4)
PEON
PE[r]ON (president, loses heart)
28. Judge soldier’s painting reflected in winning move (10)
MAGISTRATE
(GIS (soldier's) + (ART)< (painting, <reflected)) in MATE (winning move)
DOWN
2. Keep slice of Pecorino cold in river (7)
ORINOCO
[pec]ORINO CO[ld] (slice of)
3. Ghost of saint raised in the underworld (5)
SHADE
HADES (underworld, S (saint) raised)
4. I’m better after digesting poison (8)
EMBITTER
(IM BETTER)* (*after digesting)
5. Be assumed to leave quietly? (2,7,6)
GO WITHOUT SAYING
6. Perhaps pets volunteer (4-2)
STEP-UP
STEP-UP cryptically defining (perhaps) "pets"
7. Lacking iodine, outer skin’s damaged as result of overexposure (9)
SUNSTROKE
(OUTER SK[i]NS (lacking I (iodine))* (*damaged)
8. At home, dream of childhood (7)
INFANCY
IN (at home) + FANCY (dream)
14. British administration puts weight on sport (9)
BADMINTON
B (British) + ADMIN (administration) puts TON (weight) on
16. English child is clumsy in Scottish dancing (8)
CEILIDHS
(E (English) + CHILD IS)* (*clumsy)
18. Calm down after seeing headless rat in station (7)
PLACATE
[r]AT (headless) in PLACE (station)
20. Enchantment to block out the sun? (7)
DELIGHT
Double (cryptic?) definition
DE-LIGHT = block out the sun
21. Sufficient people question alternative before hesitation (6)
QUORUM
QU (question) + OR (alternative) + UM (hesitation)
24. Supply sulphur-free sugar (5)
CATER
CA[s]TER (sugar, S (sulpher) free)
Same experience as our blogger. I managed to put the consonants in the correct order for the unknown ‘pig’ at 22a (extraordinary looking creature) and had to go through the alphabet to get MICA, also my last in.
AUNT as an ‘elderly female relative’? Hmm…
Thanks to Phssthpok for an enjoyable start to the week and to Teacow
I echo your thoughts, Wordplodder; I didn’t exactly consider myself elderly or crabby on becoming an aunt, aged 27! Perhaps our setter had Bertie Wooster’s Aunt Agatha in mind?
Couldn’t get MICA without online help but I liked many of the other clues of which BOWIE KNIFE and THE BENDS were favourites.
Thanks to Teacow and Phsstpok.
Got BABIRUSA just from the anagram fodder and crossers, but failed on PEON (nho and couldn’t work it out). Enjoyed the puzzle in spite of the DNF, though.
Thanks to both.
The explanation I finally came up with for 6d is that STEP is PETS turned UP. Perhaps a bit desperate.
Thanks for the blog , I did not know BABIRUSA but I thought it was well clued for an obscure word, also MICA and PEON , nice to see a president not being from the USA.
Agree with WordPlodder and Diane that the elderly was not needed for the aunt, although they often seem to be elderly in literature as Diane mentions.
I thought this was full of good clues and will pick SOMBRERO as my favourite.
A bit challenging in places but we got there with a bit of help (help, not cheating). MICA was one of our first ones in, but we had tobrush up our rusty Spanish to recall PEÓN. BABIRUSA was new to us but easily tracked down in Chambers and we liked the improbability suggested by the surface of the clue.
DarkestDorset@4: Nothing desperate at all – we saw that as the obvious parsing.
Thanks, Phssthpok and Teacow.
Lots to like including ONYX, LOCALS, STEP-UP, SOMBRERO, and DELIGHT; two unknowns guessed correctly — BABIRUSA, CEILIDHS; two stumpers — SHADE which I might have seen in another hour or so and MICA which never would have dropped. All in all, a satisfying crossword. Thanks Phssthpok, and Teacow for parsing, especially for explaining THE BENDS that I entered by definition alone.
Thanks Phssthpok and Teacow
Funny how we all think – MICA was my first in from definition, and although I had written MIC (‘audio equipment’ + A (‘first piece of audio’), didn’t think of the clever MIC A, MIC B, etc. Didn’t see the ’round the bend’ / ‘crazy’ bit of 19a, but it just had to be.
Was another who got the pig from mixing around the ‘rabbi’ consonants in the most logical way and checking the dictionary to see if such an animal existed. Initially wrote in BOBSLEDGES at 1a until I just couldn’t parse it and eventually the SLEIGH / ‘slay’ penny dropped.
Parsed STEP-UP the same as DarkestDorset and allan.
Finished in the SE corner with LOCAL (LO-CAL taking ages to come to mind), CATER (had to check that it wasn’t CASTOR sugar) and CEILIDHS the last one in.
Nice puzzle which surprisingly didn’t take as long on the clock to finish as what it felt like to get there.