Brother of Cain and Seth (4)
I believe the answer is:
abel
'brother of cain and seth' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for abel that I've seen before include "Old Testament brother" , "Brother killed by Cain" , "Cain's victim; - Magwitch (Great Expectations)" , "character in the Bible" , "one killed early" .)