Clue: Send back dessert, a hot sort of sponge (6)
Answer: LOOFAH
Explanation: Definition: sort of sponge
A charade of LOOF, a reversal ('send back') of FOOL ('dessert') plus 'a' plus H ('hot'). A loofah or luffa is the fibrous skeleton of a cucumber-like fruit,and serves for the scrubbing function of a sponge.