Announce assuredly (4)
I believe the answer is:
aver
'announce assuredly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aver that I've seen before include "State (to be the case)" , "Maintain - state" , "Prove to be true" , "claim" , "State firmly - don't rave" .)