Giant bird given a name (5)
I believe the answer is:
titan
'giant' is the definition.
(titans are giant mythological creatures)
'bird given a name' is the wordplay.
'bird' becomes 'tit' (tit is a kind of bird).
'given' says to put letters next to each other.
'name' becomes 'n' (common abbreviation e.g. on forms).
'tit'+'a'+'n'='TITAN'
(Other definitions for titan that I've seen before include "Taint in old Greek god" , "Giant god of Gr. myth" , "Giant of Greek mythology" , "Old giant" , "Atlas, say" .)