Enclosures for the birds (4)
I believe the answer is:
pens
I believe this is a double definition.
'enclosures' is the first definition.
(pen is a kind of enclosure)
'birds' is the second definition.
(pen is a female swan)
'for the' acts as a link.
(Other definitions for pens that I've seen before include "stalls" , "Imprisons" , "Dashes off" , "Livestock enclosures" , "Writing implements" .)