Head sliced from tasteless fish, for scrap (6)
I believe the answer is:
affray
'for scrap' is the definition.
(thesaurus)
'head sliced from tasteless fish' is the wordplay.
'head sliced from' means to remove the first letter.
'tasteless' becomes 'naff' (I've seen this before).
'fish' becomes 'ray' (ray is a kind of fish).
'naff' with its initial letter taken away is 'aff'.
'aff'+'ray'='AFFRAY'
(Other definitions for affray that I've seen before include "Brawling" , "Disturbance in public place" , "Noisy quarrel" , "Disturbance of the peace" , "public brawl" .)