Enclosure holding a male or female bird (6)
I believe the answer is:
peahen
'female bird' is the definition.
(I've seen this before)
'enclosure holding a male' is the wordplay.
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'holding' indicates putting letters inside.
'male' becomes 'he' (he refers to a man).
'a'+'he'='ahe'
'pen' enclosing 'ahe' is 'PEAHEN'.
'or' acts as a link.
(Other definitions for peahen that I've seen before include "Female bird (with a proud partner?)" , "Female of a show-off bird" , "Female of the large bird, Pavo species" , "Female fowl with a resplendent mate" , "Drab bird" .)