Examiner, verifier (7)
I believe the answer is:
checker
This clue is a double definition.
'examiner' is the first definition.
(I know that checker is a type of examiner)
'verifier' is the second definition.
(I've seen this before)
(Other definitions for checker that I've seen before include "one dispatched to vet?" , "a man in America" , "Assessor" , "Verifier" , "Scrutiniser" .)