Topless yellow bird (5)
I believe the answer is:
raven
'bird' is the definition.
(raven is a kind of bird)
'topless yellow' is the wordplay.
'topless' means to remove the first letter.
'yellow' becomes 'craven' (both can mean cowardly).
'craven' with its first letter removed is 'RAVEN'.
(Other definitions for raven that I've seen before include "Black crow" , "Bird of ill omen" , "Passerine bird" , "Hungrily devour" , "Poe's poetic bird" .)