Perhaps setter's gonna tune out (5,4)
I believe the answer is:
agent noun
'perhaps setter's' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'gonna tune out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'gonna'+'tune'='gonnatune'
'gonnatune' is an anagram of 'AGENT NOUN'.
Can you help me to learn more?
(Other definitions for agent noun that I've seen before include "lecturer, say" , "leader, perhaps" , "Writer is one" , "lecturer, for instance" .)