Cold dessert and hot served up for old folk (5)
I believe the answer is:
iceni
'old folk' is the definition.
(ancient tribe of Britain)
'cold dessert and hot served up' is the wordplay.
'cold dessert' becomes 'ice' (eg an ice lolly).
'and' is a charade indicator (letters next to each other).
'hot' becomes 'in' (both can mean fashionable).
'served up' is a reversal indicator (in a down clue, going upwards).
'in' written backwards gives 'ni'.
'ice'+'ni'='ICENI'
'for' acts as a link.
(Other definitions for iceni that I've seen before include "British people once" , "people rebelling against Rome" , "Old tribe" , "Old people" , "Boudica's tribe" .)