Brother of Isaac (4)
I believe the answer is:
esau
'brother of isaac' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for esau that I've seen before include "Old Testament twin" , "Birthright seller (Bible)" , "Jacob's twin brother" , "Elder of the twin sons of Isaac and Rebecca" , "Old Testament character sounds as if he had a vision" .)