Sharp dessert (4)
I believe the answer is:
tart
I believe this is a double definition.
'sharp' is the first definition.
(I know that sharp can be written as tart)
'dessert' is the second definition.
(type of dessert)
(Other definitions for tart that I've seen before include "Sour -- acid" , "Sour-tasting pie?" , "Flan; acidic" , "Sharp; pastry" , "Biting; flan" .)