His is a search examination, by all accounts (7)
I believe the answer is:
auditor
'his is a search' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'examination by all accounts' is the wordplay.
'examination' becomes 'audit' (I've seen this before).
'by all accounts' becomes 'or' (I can't explain this - if you can you should believe this answer much more).
'audit'+'or'='AUDITOR'
Can you help me to learn more?
(Other definitions for auditor that I've seen before include "Financial checker" , "One reviewing books" , "One inspects the accounts" , "He'll check the accounts" , "Accounts inspector" .)