Forefather in scorn ate bananas (8)
I believe the answer is:
ancestor
'forefather' is the definition.
(I've seen this before)
'scorn ate bananas' is the wordplay.
'bananas' is an anagram indicator (informal term for mad).
'scorn'+'ate'='scornate'
'scornate' anagrammed gives 'ANCESTOR'.
'in' acts as a link.
(Other definitions for ancestor that I've seen before include "Person from whom one is descended" , "Antecedent, forebear" , "An escort (anag.)" , "Predecessor" , "Adam was our first one" .)