Trade union participating in exchange study (4,2)

I believe the answer is:

swot up

'study' is the definition.
(swotting up is a kind of studying)

'trade union participating in exchange' is the wordplay.
'trade union' becomes 'TU' (abbreviation for trade union).
'participating in' means one lot of letters goes inside another.
'exchange' becomes 'swop' (swop is a kind of exchange).
'tu' put into 'swop' is 'SWOT UP'.

(Another definition for swot up that I've seen is " Revise".)

I've seen this clue in The Independent.

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