Old-fashioned stuff, but it may be sweet (4)

I believe the answer is:

corn

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'old-fashioned stuff' is the definition.
'corn' can be an answer for 'stuff' (thesaurus). I am not certain of the 'old-fashioned' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for corn that I've seen before include "Cereal crop; callus" , "Painful affliction" , "Crop - growth" , "Something unoriginal - cereal plant" , "Hard thickening of the skin on a toe" .)

I've seen this clue in the Evening Standard.

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