In brownish-red, a cold biscuit (8)
I believe the answer is:
macaroon
'biscuit' is the definition.
(macaroon is a kind of biscuit)
'in brownish-red a cold' is the wordplay.
'in' is an insertion indicator.
'brownish red' becomes 'maroon' (I've seen this before).
'a cold' becomes 'ac' (I've seen this in other clues).
'maroon' placed around 'ac' is 'MACAROON'.
(Other definitions for macaroon that I've seen before include "Something nutty to enjoy" , "Sweet almond biscuit" , "Biscuit of egg-white and almonds or coconut" , "Almond or coconut biscuit" , "Light biscuit" .)