Pale, like chicken (5)
I believe the answer is:
ashen
'pale' is the definition.
('ashen' can be a synonym of 'pale')
'like chicken' is the wordplay.
'like' becomes 'as'.
'chicken' becomes 'hen' (hen is a kind of chicken).
'as'+'hen'='ASHEN'
(Other definitions for ashen that I've seen before include "Bloodless" , "Pale (with shock/illness)" , "Wan - wooden - pallid" , "Grey, pallid" , "Anaemic looking" .)