Attest (6)
'attest' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for affirm that I've seen before include "Ratify; vouch" , "State as a fact, assert" , "State as a fact, perhaps in court" , "Avow or corroborate" , "Declare one's commitment (to)" .)
'attest' is the definition.
(I know that attest is a more specific form of avow)
This is the entire clue.
(Other definitions for avow that I've seen before include "Declare - admit" , "Assert/confess openly" , "Declare - affirm" , "Solemnly declare" , "acknowledge" .)
'attest' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aver that I've seen before include "State firmly, maybe rave" , "Swear" , "State firmly, perhaps rave" , "Firmly maintain" , "State firmly, declare" .)