Bears witness (7)
I believe the answer is:
attests
'bears witness' is the definition.
('attest' can be a synonym of 'bear witness')
This is all the clue.
(Other definitions for attests that I've seen before include "Gives evidence in court" , "Bears witness" , "Sat test (anag.)" , "Certifies" , "Authenticates or affirms to be true" .)