A dessert is served up cold (5)
I believe the answer is:
aloof
'cold' is the definition.
('aloof' can be a synonym of 'cold')
'a dessert is served up' is the wordplay.
'dessert' becomes 'fool' (I've seen this before).
'is served up' says the letters should be written backwards.
'fool' in reverse letter order is 'loof'.
'a'+'loof'='ALOOF'
(Other definitions for aloof that I've seen before include "Coldly distant" , "Showing detached attitude" , "Displaying supercilious reserve" , "Unpleasantly cold" , "Detached, distant" .)