Bird has two parties (4)
I believe the answer is:
dodo
'bird' is the definition.
(dodo is a kind of bird)
'two parties' is the wordplay.
'two parties' can mean two replacements for 'party'.
'party' becomes 'do' (do is a kind of party).
'party' becomes 'do' (do is a kind of party).
'do'+'do'='DODO'
'has' is the link.
(Other definitions for dodo that I've seen before include "Native of Mauritius" , "Repetitive extinct animal" , "Flightless bird, extinct since the 17th century" , "Large extinct bird" , "silly person" .)