Biblical man who sold his birthright for a mess of pottage (4)
I believe the answer is:
esau
'biblical man who sold his birthright for a mess of pottage' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for esau that I've seen before include "Jacob's twin brother" , "character in the Bible" , "Twin brother of Jacob" , "Hairy biblical man" , "Old Testament twin" .)