Electra's brother (7)
I believe the answer is:
orestes
'electra's brother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for orestes that I've seen before include "Matricide" , "figure in Greek tragedy" , "Brother of Electra; so terse (anag.)" , "Killer of mother" , "Son of Agamemnon" .)