Variety of duck (7)
I believe the answer is:
mallard
'variety of duck' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for mallard that I've seen before include "Variety of duck" , "Common wild duck" , "web-footed bird" , "Type of duck - world speed record holding steam engine (1938)" , "Oldest breed of duck" .)