One departing from majority line upset residents (9)
I believe the answer is:
dissenter
'one departing from majority line' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'upset residents' is the wordplay.
'upset' indicates an anagram.
'residents' anagrammed gives 'DISSENTER'.
Can you help me to learn more?
(Other definitions for dissenter that I've seen before include "Nonconformist" , "One who disagrees out of tiredness" , "A non-orthodox" , "One expressing disagreement" , "One who objects" .)