Poser leaves sour grapes for something sweet (5)

I believe the answer is:

sugar

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'something sweet' is the definition.

I cannot understand how the rest of the clue works.

(Other definitions for sugar that I've seen before include "Basic sweetener" , "--- Ray Robinson, boxer" , "Make more palatable" , "Sucrose" , "Sweetening agent" .)

I've seen this clue in the Irish Times.

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