Almost dressing a bird (5)
I believe the answer is:
robin
'a bird' is the definition.
(robin is a kind of bird)
'almost dressing' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'dressing' becomes 'robing' (robing is a kind of dressing).
'robing' with its final letter taken away is 'ROBIN'.
(Other definitions for robin that I've seen before include "Popular British bird" , "Day was one" , "Bird on many cards" , "Bird - one in Lincoln green?" , "Small brown thrush" .)