Bird, yellow, heading off (5)
I believe the answer is:
raven
'bird' is the definition.
(raven is a kind of bird)
'yellow heading off' is the wordplay.
'yellow' becomes 'craven' (both can mean cowardly).
'heading off' means to remove the first letter.
'craven' with its first letter taken away is 'RAVEN'.
(Other definitions for raven that I've seen before include "Type of crow" , "Bird in 1's poem" , "flesh-eating bird" , "Crow-like bird" , "Voraciously eat" .)