Heated small fish that's wrapped (5)
I believe the answer is:
fiery
'heated' is the definition.
(synonyms)
'small fish that's wrapped' is the wordplay.
'small fish' becomes 'fry' (I've seen this before).
'that's' becomes 'ie'.
'wrapped' indicates putting letters inside.
'fry' placed around 'ie' is 'FIERY'.
(Other definitions for fiery that I've seen before include "Explosive (e.g. temper)" , "Quick-tempered" , "Easily angered" , "Choleric" , "Intensely hot" .)