Bridge partners declare, having the bird (6)
I believe the answer is:
weaver
'the bird' is the definition.
(weaver is a kind of bird)
'bridge partners declare' is the wordplay.
'bridge partners' becomes 'we' (West and East are players in the card game bridge).
'declare' becomes 'aver' (averring is a kind of declaring).
'we'+'aver'='WEAVER'
'having' acts as a link.
(Other definitions for weaver that I've seen before include "Fabric maker" , "He makes cloth or fabric" , "Person who works a loom" , "Bottom's trade in A M N D" , "A craftsman" .)