Fool, possibly, principally serving in arid waste (7)

I believe the answer is:

dessert

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'fool possibly' is the definition.
(fool is a type of dessert)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for dessert that I've seen before include "Sweet, afters" , "End of meal" , "Spotted Dick is one" , "Sweet, last course of a meal" , "tart?" .)

I've seen this clue in The Times.

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