Visibly frightened: like chicken? (5)
I believe the answer is:
ashen
'visibly frightened' is the definition.
(I've seen this in another clue)
'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 "(Of face) pale (with shock)" , "Unhealthily pale" , "bleached" , "Pale (with shock/illness)" , "Greyish" .)