Jacob's brother gets vague in the evening (4)
I believe the answer is:
esau
'jacob's brother' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for esau that I've seen before include "Biblical twin to Jacob" , "Jacob's brother (OT)" , "Cheated brother" , "Jacob's brother (Gen.)" , "Hairy OT man" .)