He expresses his objections, but is in favour of examiner (9)
I believe the answer is:
protester
'he expresses his objections but' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in favour of examiner' is the wordplay.
'in favour of' becomes 'pro' (being pro a particular cause).
'examiner' becomes 'tester' (synonyms).
'pro'+'tester'='PROTESTER'
'is' is the link.
Can you help me to learn more?
(Other definitions for protester that I've seen before include "Person, we hear, not content" , "objector" , "I strongly object" , "Dissident" , "Demonstrator" .)