Crystalline carbohydrate (5)
I believe the answer is:
sugar
'crystalline carbohydrate' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sugar that I've seen before include "Mild oath (granulated?)" , "Make more palatable" , "rotter!" , "Argus (anag.)" , "Basic sweetener" .)