Shared with mammal (4)
I believe the answer is:
hare
'mammal' is the definition.
(I have seen 'Swift mammal ' mean 'hare' so perhaps 'mammal' could also mean 'hare')
'shared with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'HARE' is hidden within 'shared'.
(Other definitions for hare that I've seen before include "'You can't run with the . . . . and hunt with the hounds'" , "Fast runner" , "Old saying: 'Let the .... sit" , "Small rabbit-like mammal" , "Game, -- and hounds" .)