Trace son in order to reveal forefather (8)
I believe the answer is:
ancestor
'forefather' is the definition.
(thesaurus)
'trace son in order' is the wordplay.
'in order' is an anagram indicator (the letters in a new order).
'trace'+'son'='traceson'
'traceson' with letters rearranged gives 'ANCESTOR'.
'to reveal' acts as a link.
(Other definitions for ancestor that I've seen before include "One of one's forebears" , "not being of the modern generation" , "An escort (anag.)" , "Person from whom one is descended" , "Adam was our first one" .)