Pasty, like a bird (5)
I believe the answer is:
ashen
'pasty' is the definition.
(both can mean pale)
'like a bird' is the wordplay.
'like' becomes 'as'.
'a bird' becomes 'hen' (hen is a kind of bird).
'as'+'hen'='ASHEN'
(Other definitions for ashen that I've seen before include "may be pale with shock" , "Shane (anag.)" , "Anaemic-looking" , "Pale (with shock/illness)" , "Pale-faced" .)