Deadly pale, like a bird (5)
I believe the answer is:
ashen
'deadly pale' is the definition.
(I've seen this in another clue)
'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" , "Grey-faced" , "Bloodless" , "Visibly shocked" , "Greyish" .)