Car having rust upset examiner (7)
I believe the answer is:
auditor
'examiner' is the definition.
(an auditor examines accounts etc)
'car having rust upset' is the wordplay.
'car' becomes 'audi' (audi is a german car brand).
'having' is a charade indicator (letters next to each other).
'rust' becomes 'rot'.
'upset' shows that the letters should be reversed in order.
'rot' reversed gives 'tor'.
'audi'+'tor'='AUDITOR'
(Other definitions for auditor that I've seen before include "Accountant - listener" , "Account inspector" , "Financial checker" , "Listener; checker" , "He checks the account books annually" .)