Puzzle's answer about potato dish, cold (8)
I believe the answer is:
acrostic
'puzzle's' is the definition.
(I've seen this before)
'answer about potato dish cold' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'about' becomes 'c' (abbreviation for 'circa').
'potato dish' becomes 'rosti' (I've seen this before).
'cold' becomes 'c' (eg on taps).
'a'+'c'+'rosti'+'c'='ACROSTIC'
(Other definitions for acrostic that I've seen before include "Poem with word(s) reading downwards" , "Socratic kind of old word puzzle" , "Puzzle spelling out something with first letters" , "problem" , "Poem where first letters of lines spell a word" .)