Hero's hero? (7)
I believe the answer is:
leander
'hero's hero?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for leander that I've seen before include "Oarsmen" , "Hero's lover; rowing club" , "Heroic lover" , "Learned like Hero's lover in Greek legend" , "Ill-fated lover" .)