Form of aspic with sweet pepper (8)
I believe the answer is:
capsicum
'sweet pepper' is the definition.
(I've seen this before)
'form of aspic with' is the wordplay.
'form of' is an anagram indicator (another form of the same letters).
'with' becomes 'cum' ('with' in Latin).
'aspic' is an anagram of 'capsi'.
'capsi'+'cum'='CAPSICUM'
(Other definitions for capsicum that I've seen before include "something pungent" , "American pepper" , "hot stuff perhaps" , "Eg, chilli pepper" , "Pepper fruit" .)