Swan enclosure (3)
I believe the answer is:
pen
I believe this is a double definition.
'swan' is the first definition.
(pen is a kind of swan)
'enclosure' is the second definition.
(pen is a kind of enclosure)
(Other definitions for pen that I've seen before include "Shut up" , "Pound" , "'The ... is mightier than the sword'" , "Writing implement" , "Coop" .)