Swift mammal (4)
I believe the answer is:
hare
'swift mammal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hare that I've seen before include "Swift mammal" , "Swift rodent" , "Game, -- and hounds" , "Herbivore" , "'Swift, long-eared animal (4)'" .)