Trade farthings or shillings? (8)

I believe the answer is:

exchange

'trade' is the definition.
(exchange of items)

I can't explain the remainder of the clue.

(Other definitions for exchange that I've seen before include "Swap, barter" , "market" , "Convert" , "Bandy" , "Altercation" .)

I've seen this clue in The Times.

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