Bird on the Mexican flag (5)
I believe the answer is:
'bird on the mexican flag' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eagle that I've seen before include "The emblem of the US is bald" , "Keen-eyed bird" , "Bird - emblem of power" , "Bird of prey; former children's comic" , "somewhat under par" .)