Contradict key judgement (6)

I believe the answer is:

belief

'judgement' is the definition.
(thesaurus)

'contradict key' is the wordplay.
'contradict' becomes 'belie' ('belie' can be a synonym of 'contradict').
'key' becomes 'f' (I've seen this in other clues**).
'belie'+'f'='BELIEF'

(Other definitions for belief that I've seen before include "Persuasion" , "Creed or opinion" , "Tenet, creed" , "Conviction, faith" , "Religious conviction" .)

I've seen this clue in the Irish Times.

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