Cain and Abel's brother (4)
I believe the answer is:
seth
'cain and abel's brother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for seth that I've seen before include "Adam and Eve's third son" , "Vikram --, Indian author" , "One of the first men" , "Third son of Adam and Eve" , "Early human" .)