Mental activity is pre-empted by votes against (6)

I believe the answer is:

noesis

'mental activity' is the definition.
(noesis means thought or mental activity)

'is pre-empted by votes against' is the wordplay.
'pre-empted by' says to put letters next to each other (some letters go before others).
'votes against' becomes 'noes' ('no' votes).
'is' after 'noes' is 'NOESIS'.

I've seen this clue in The Guardian.

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