Brother of Cain (4)
I believe the answer is:
abel
'brother of cain' 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 "done in before anyone else" , "murdered second son?" , "Cain's younger brother" , "Cain's 11" , "fellow killed by brother" .)