Dressin' the Christmas bird? (5)
I believe the answer is:
robin
I believe this clue is a double definition.
'dressin'' is the first definition.
('robing' said like 'dressing' was; robing is a kind of dressing)
'the christmas bird?' is the second definition.
(I've seen this before)
(Other definitions for robin that I've seen before include "Day was one" , "Christmas songbird" , "Garden bird" , "Popular British bird" , "Red-breasted songbird" .)