Buying and selling ingredients for jam? (7)

I believe the answer is:

traffic

'buying and selling' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for traffic that I've seen before include "Movement along a route" , "Deal illegally , in drugs say" , "Illegal trading" , "Illegally push" , "Deals" .)

I've seen this clue in The Everyman puzzle in The Observer.

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