Bird gets very cold heading north (7)
I believe the answer is:
bittern
'bird' is the definition.
(bittern is a kind of bird)
'very cold heading north' is the wordplay.
'very cold' becomes 'bitter' (bitter informally can mean very cold).
'heading north' becomes 'n' (abbreviation).
'bitter'+'n'='BITTERN'
'gets' is the link.
(Other definitions for bittern that I've seen before include "inhabitant of marsh" , "'He shall not hear the . . . cry' (Ledwidge)" , "large wader" , "Wading bird" , "''He shall not hear the ... cry / In the wild sky where he is lain'' (Lament for Thomas MacDonagh)" .)