Twin who sold his birthright (4)
I believe the answer is:
esau
'twin who sold his birthright' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for esau that I've seen before include "Biblical twin to Jacob" , "wronged brother" , "man tricked by kid brother" , "Brother to Jacob (OT)" , "Biblical character who sold birthright for pottage" .)