Enclosure for female swan (3)
I believe the answer is:
pen
This clue is a double definition.
'enclosure' is the first definition.
(I know that pen is a type of enclosure)
'female swan' is the second definition.
(I've seen this in another clue)
'for' is the link.
(Other definitions for pen that I've seen before include "record" , "Coop" , "International Association of poets, playwrights etc" , "Writing instrument" , "dash off" .)