Forefather in scorn ate nuts (8)
I believe the answer is:
ancestor
'forefather' is the definition.
(I've seen this before)
'scorn ate nuts' is the wordplay.
'nuts' is an anagram indicator (nuts can mean crazy).
'scorn'+'ate'='scornate'
'scornate' is an anagram of 'ANCESTOR'.
'in' is the link.
(Other definitions for ancestor that I've seen before include "Person from whom one is descended" , "Antecedent, forebear" , "Predecessor" , "not being of the modern generation" , "descent comes from one" .)