Trade in former money (8)

I believe the answer is:

exchange

'trade in' is the definition.

'former money' is the wordplay.
'former' becomes 'ex'.
'money' becomes 'change' (I've seen this before**).
'ex'+'change'='EXCHANGE'

(Other definitions for exchange that I've seen before include "'Swap, trade (8)'" , "Substitute" , "Stock trading site" , "Give one thing and get another back" , "market" .)

I've seen this clue in The Telegraph.

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