Nut? It is a chop that’s cooked (9)
I believe the answer is:
pistachio
'nut?' is the definition.
(I know that pistachio is a type of nut)
'it is a chop that's cooked' is the wordplay.
'it is' becomes 'itis'.
'that's cooked' is an anagram indicator (letters cooked into a new form).
'itis'+'a'+'chop'='itisachop'
'itisachop' is an anagram of 'PISTACHIO'.
(Other definitions for pistachio that I've seen before include "nut-bearing tree" , "Edible pale green seed" , "Edible nut" , "Food" , "Type of nut" .)