Bird on the Canadian dollar coin (4)
I believe the answer is:
loon
'bird on the canadian dollar coin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loon that I've seen before include "Fool" , "Diver; silly person" , "Noddy" , "Simple-minded person" , "Fish-eating diving bird" .)