Cake coating (5)
I believe the answer is:
icing
'cake coating' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for icing that I've seen before include "Sugar-coating" , "unwelcome on aircraft" , "effect of cold weather" , "Sugar coating - a danger to aircraft, on roads etc" , "Sugary topping" .)