Jacob's biblical brother (4)
I believe the answer is:
esau
'jacob's biblical brother' 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 "Jacob's brother (OT)" , "Isaac's eldest son" , "Jacob's twin (Bible)" , "Isaac's hairy son" , "Biblical character who sold birthright for pottage" .)