Adam's second son (4)
I believe the answer is:
abel
'adam's second son' 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 "Cain's victim; - Magwitch (Great Expectations)" , "done in before anyone else" , "Biblical murder victim" , "Cain slew him" , "Cain's murdered brother" .)