Bird back after leaving Sweden (4)
I believe the answer is:
tern
'bird' is the definition.
(tern is a kind of bird)
'back after leaving sweden' is the wordplay.
'back' becomes 'stern' (I've seen this before).
'after leaving' indicates named letters should be taken away.
'sweden' becomes 's'.
'stern' with 's' removed is 'TERN'.
(Other definitions for tern that I've seen before include "Seagull" , "Small seabird with forked tail" , "Three-masted schooner" , "Rent out the bird" , "Pay rent for seabird" .)