Pop group starts to get extra stroppy after cold vegetables (8)
I believe the answer is:
cabbages
'vegetables' is the definition.
(cabbage is a kind of vegetable)
'pop group starts to get extra stroppy after cold' is the wordplay.
'pop group' becomes 'abba' (I've seen this before**).
'starts to' indicates taking the first letters.
'after' is a charade indicator (letters next to each other).
'cold' becomes 'c' (eg on taps).
The initial letters of 'get extra stroppy' is 'ges'.
'abba'+'ges'='abbages'
'abbages' after 'c' is 'CABBAGES'.
(Other definitions for cabbages that I've seen before include "Begs a cab to get vegetables" , "heads for kitchen" , "Members of the Brassica family" , "Of shoes and ships and ceiling wax,/ of . . . . . . . . and kings (Through the Looking Glass)" , "Brassicas" .)