Thanks to Monk for the challenge.
Great fun! A few new words for me today. We have both Toscanini and Puccini on opposite sides of the grid (they apparently had a tempestuous friendship), but I don’t see more to it. The grid contains a pangram which is always a nice touch. Many thanks to Monk!

E.G.< (maybe, <retiring) + (SAGE (wise guy) on T (tense) + THEMES (subjects))
STEPS ON (moves against)
‘Issue’ meaning child in this context
CONE (solid object) securing SUM (whole)
Double definition
(TOXIN DATA IN)* (*aberrant)
LEAD IN (intro) before (QUOTING* (*rubbish) about E (English) + S (society))
JACK IN (ditch) + THE PULPIT (above which cloth may go)
EVER (at any time) in (A DISNEY)* (*complex)
CO2 (colourless, odourless gas) expanded
LOO (place to go) around (RE (on) + NZ (New Zealand))
A reference to Shakespeare’s Merchant of Venice perhaps?
[sop]ORIFIC E[legy] (section of)
OPPO (cohabitee) + (I INSTRUCT)* (*somehow)
ELECT (choose) + RA (artist)
TOSCA (opera) joining [me]N IN I[olanthe] (quartet of)
[st]ERN (rigorous, putting ST (good man, saint) down)
Max Ernst is a German artist of the Dada and Surrealist movements.
(RULES ONCE)* (*broken)
SIN (function) on AI (e.g. Claude)
Claude is one Artificial Intelligence application
Mount Sinai is biblical – the place where Moses received the ten commandments written on stone tablets
G (good) + AMI (friend, from French) catching OUR (setter’s and solvers’)
ASP (snake) with (LETHAL* (*bent) bites JUNG (psychologist))
Double definition
The second definition is self-explanatory, and the first British slang for male genitalia
STAGE* (*shifted) ahead of BOUT (fight?)
(IS NERVOUS)* (*criminal)
Australian dialect uses the word ‘souvenir’ as a verb meaning to steal something – usually something small
OVER (several deliveries, cricket) in CUP (container)
(IN + I (international) + C (clubs) + CUP (trophy))< (<being lifted)
RO[b] (nick, almost) keeps ONE (individual)
R (Republican) wearing DOWN (blue)
[16d … like the Lufthansa ashtray we have that somebody once souvenired from an airport lounge]