Is their behaviour revolting? (7)

I believe the answer is:
rioters
'is their' is the definition.
I can't tell whether this defines the answer.
'behaviour revolting?' is the wordplay.
'behaviour' becomes 'riot' (I have seen 'Rowdy behaviour ' mean 'riot' so perhaps 'behaviour' could also mean 'riot').
'revolting?' becomes 'ers' (I can't justify this - if you can you should believe this answer much more).
'riot'+'ers'='RIOTERS'
Can you help me to learn more?
(Other definitions for rioters that I've seen before include "Violent troublemakers" , "Rabble-rousers" , "They disturb the peace" , "Demonstrators" , "Crowd disturbing the peace" .)
