Frosting (5)
I believe the answer is:
icing
'frosting' is the definition.
(I know that frosting can be written as icing)
This is the entire clue.
(Other definitions for icing that I've seen before include "it's dangerous on the roads" , "Cake-topper" , "Cake covering" , "Freezing" , "Topping in a bag" .)