One wearing top up in sun rejected counteractive measures (10)

I believe the answer is:

nullifiers

'counteractive measures' is the definition.

'one wearing top up in sun rejected' is the wordplay.
'one' becomes 'i' (Roman numeral**).
'wearing' indicates putting letters inside.
'top up' becomes 'refill'.
'in' indicates putting letters inside.
'rejected' is a reversal indicator.
'refill' put into 'sun' is 'srefillun'.
'i' put into 'srefillun' is 'sreifillun'.
'sreifillun' reversed gives 'NULLIFIERS'.

I've seen this clue in The Independent.

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