Witness a time trial (6)

I believe the answer is:

attest

'witness' is the definition.
(thesaurus)

'a time trial' is the wordplay.
'time' becomes 't'.
'trial' becomes 'test' ('test' can be a synonym of 'trial').
'a'+'t'+'test'='ATTEST'

(Other definitions for attest that I've seen before include "Offer evidence" , "Confirm to be true" , "Bear formal witness to, give evidence" , "Verify" , "Give sworn evidence" .)

I've seen this clue in The Telegraph.

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