Mammal with webbed feet (5)
I believe the answer is:
otter
'mammal with webbed feet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for otter that I've seen before include "Freshwater brown carnivore" , "Fish-eater of the weasel family" , "Lithe swimmer" , "Aquatic member of weasel family" , "Tarka, for one" .)