Topped with frosting (4)
I believe the answer is:
iced
'topped with frosting' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for iced that I've seen before include "Having a sugary coating" , "Took out" , "Frozen, chilled" , "hidden under white crystals?" , "Decorated with sugary mixture" .)