When female, is white (5)
I believe the answer is:
ashen
'is white' is the definition.
(I've seen this before)
'when female' is the wordplay.
'when' becomes 'as'.
'female' becomes 'hen' (hen is a kind of female**).
'as'+'hen'='ASHEN'
(Other definitions for ashen that I've seen before include "Livid" , "(Of face) pale with fear" , "Grey, pallid" , "Drained of colour" , "White" .)