Poser leaves sour grapes for something sweet (5)

I believe the answer is:

sugar

I'm a little stuck... Click here to teach me more about this clue!

'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.

Want a hint initially instead of a full solution? Install my app