Icing the problem? A rug's perhaps the answer (5)
I believe the answer is:
sugar
'icing' is the definition.
(icing sugar is a type of sugar)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sugar that I've seen before include "Basic sweetener" , "Common sweetener" , "Damn" , "Plantation product" , "rotter!" .)