Eg, mallard (4)
I believe the answer is:
duck
'eg mallard' is the definition.
(I know that Anas platyrhynchos is a type of duck)
This is all the clue.
(Other definitions for duck that I've seen before include "Water bird; zero score" , "Zero score; avoid" , "Quacker?" , "Mallard, say, or eider" , "Waterbird" .)