Chocolate, perhaps, for Chesterton's father (5)
I believe the answer is:
brown
I believe this is a double definition.
'chocolate perhaps' is the first definition.
(chocolate is a kind of brown)
'chesterton's father' is the second definition.
(GK Chesterton character Father Brown)
'for' acts as a link.
(Other definitions for brown that I've seen before include "Dark - tanned - successor to Blair?" , "Colour; ex-PM" , "After half portion of bran, have" , "Former PM" , "Colour - grill lightly" .)