Confirmation (13)
'confirmation' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for proof that I've seen before include "Measure of the strength of alcohol" , "Trial printing" , "Exposition ending QED?" , "mathematical tour de force" , "Test" .)
'confirmation' is the definition.
(I know that corroboration is a type of confirmation)
This is the entire clue.
(Other definitions for corroboration that I've seen before include "Further proof" , "Confirmation" .)