Icing the problem? A rug's maybe the answer (5)
I believe the answer is:
sugar
'icing the problem?' is the definition.
'sugar' can be an answer for 'icing' (icing sugar is a type of sugar). I am not certain of the 'the problem?' bit.
'a rug's maybe the answer' is the wordplay.
'maybe the answer' indicates an anagram (the letters can become the answer when anagrammed).
'a'+'rugs'='arugs'
'arugs' is an anagram of 'SUGAR'.
(Other definitions for sugar that I've seen before include "Mild oath (granulated?)" , "Cane or beet product" , "Argus (anag.)" , "rotter!" , "See 11" .)