Son of Agamemnon
I believe the answer is:
orestes
'son of agamemnon' 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 "figure in Greek tragedy" , "Matricide" , "Son of Agamemnon" , "he killed his mother and her lover" , "Tragically, killer" .)