Colour about half of cake or biscuit (8)
I believe the answer is:
macaroon
'biscuit' is the definition.
(I know that Macaroon is a type of biscuit)
'colour about half of cake' is the wordplay.
'colour' becomes 'maroon' (I've seen this before).
'about' indicates putting letters inside.
'half of' means to take half the letters.
'cake' cut in half is 'ca'.
'maroon' enclosing 'ca' is 'MACAROON'.
'or' is the link.
(Other definitions for macaroon that I've seen before include "Sweet biscuit made with ground almonds" , "Biscuit made with almond paste" , "Chewy biscuit containing almond paste" , "Biscuit of egg-white and almonds or coconut" , "Almond or coconut biscuit" .)