Phew! A meaty, but quite exceptional challenge from IO.
Thanks to IO for the challenge – extremely creative, witty and fun. Certainly not 16/19, but well worth the perseverance.

ON AIR (broadcasting); BE (live) takes
CO (business) collects [ar]AUCAR[ia]* (strain extracted from, *growing wild)
R[e]AL GRUB< (authentic food, <for backsliding, scrubs E (drug))
MEN (players) + (U (united) + IN taking H[alle] (overture to))
J (Jack) + (UP A LANE)* (*molested)
“BRA’S ILL” (supporter’s misfortune, “discussed”)
CH (Switzerland) acquires ILE (island, from the French)
To understand this clue, we must have clocked the five groups hidden in the grid – as highlighted. Each group is themed and has words starting with the letters A, B, C. Masterful.
AS (like) + SASS (the impudence of Drake) + IN
Not certain on this one – ‘sassy Drake’ is a viral meme
To ‘ice’ someone is to assassinate them
V[e]A[l] R[i]B[s]< (periodically, <turned) + O (over)
(ESC (key) dresses PRO (for))< (<sent back)
CHURN (agitator) catching ([train]S (last of) + TO)
CHAR (one does) + LIE (stretch)
PENNI[n]G (composition, using only two N (note)s), receiving F (fine)
A pfennig is one hundredth of a Mark – old German currency
HEX (put the mockers on) + BILL (Spooner’s namesake) – as a Spoonerism
Bill Spooner presumably referring to the musician from The Tubes
[h]AND OVER (transfer, H (hotel) despatched)
PULE (pipe) in [b]ONCES (heads, having put away B (billion)
‘Bonce’ is UK slang for one’s head; ‘pule’ is to pipe/chirp/make a high pitched sound
R (resistance) encountered by A GENT (a man) + IN A
[p]LEA[s][u]RA[b]LE* (*brews, PUBS withdrawing)
Roger Protz is a world leading beer writer, campaigner and taster
(“EWES” (ovine females) and “A BULL” (a bovine male)) (“reportedly”)
A (academy) + R (run) + [o]U[t] B[y] A (off and on)
A (an) + LIBI[do] (urge, to leave DO (the same, ditto))
[actu]AL FA[ct] (in)
Alfa is a grassy plant used for papermaking
Double definition
Lord Privy Seal is the role of Baroness Smith of Basildon in UK parliament
([Hamilto]N (rear wing) + IS ALMOST)* (*out)
A + LOG (fine) being in POISE (balance)
Nautically, a sailor could have had his name logged for an offence for which he would be fined
(LAIC (non-churchy) + EPs (recordings))< (<uplifting)
Double definition
‘Nick’ can be slang for a police station, or a name for the devil/a bogy, as in ‘Old Nick’
FUEL* (*liquid) in BIN (apparently refused)
O (oxygen) taken up in CH[o]RE (e.g. washing or cleaning)
ORC (evil goblin) blocking PH (pub, public house)
Phew indeed. I thought I was doing well until I hit the wall in the southeast corner, which took me forever. Lesson learned about feeling too good with this setter. I did not spot the theme. Kudos to Oriel and thanks as always to Io.
Well done Oriel. A masterful blog, which I needed for several clues. A very tough puzzle but worth persevering as you said.I missed the groups for 16/19d. Bunged in LPS although I was ignorant of Lady Smith’s role. You needed to have extensive general knowledge and all your wits.
Thanks IO and Oriel.
Thanks for the blog and the coloured grid , a great effort .
Fortunately I have a lot of time on Wednesday for crosswords and started at 6 am .
A nuclear theme , very well done but perhaps more obscurity than usual . I know Devon quite well but CHURSTON is new to me . I asked in the English Faculty about JEAN PAUL , over ten people before I got someone who knew about him . Most thought it must be Sartre but that would not do .
Don’t know if Io had this in mind when constructing the surface for 19a but (Bobby) Drake is the name of the Iceman in the X-Men.
As usual, fell well short of completing this, mostly unknowns to me. I had 9 answers missing and didn’t parse LPS and couldn’t fully explain 16/19. That’s pretty good for me on an Io though.
In 29, is it possible that “his namesake” refers to Rev. William Spooner himself? He could be a Bill…
10 right today.
A new IO record for me.
Excellent puzzle. Superb blog.
Thanks Io and Oriel. You are a great pair.
Difficult to pick faves.
AS EASY AS ABC was my COTD.
While grouping, I had ASSASSIN, BURGLAR and CORPSE in one group.
I didn’t know the Sue Grafton connection. Googled after seeing the
grouping in the blog.
I thought ‘so’ referred to the solution itself. I may be wrong.
ASSASSIN
I thought about Drake in Iceman as the def (Hovis@4 took a similar route, I see).
Then ‘of’ had to stand for ‘IN’. Not sure, that is okay.
BRAZIL, USEABLE and several others were very good.