Lead killing the last pair of river birds (4)
I believe the answer is:
hero
'lead' is the definition.
(I've seen this in other clues)
I can't explain the rest of the clue.
(Other definitions for hero that I've seen before include "Valiant man" , "Main protagonist" , "object of adulation" , "Man admired for outstanding bravery" , "Exceptionally brave person" .)