Cake embellishment (5)
I believe the answer is:
icing
'cake embellishment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for icing that I've seen before include "Maybe Madeira's topping" , "Cake covering" , "Embellishing the cake" , "that finishes off 29 [ANGEL CAKE]" , "7 Across topping" .)