Idiotic one involved with insane rioting (7)
I believe the answer is:
asinine
'idiotic' is the definition.
(both can mean foolish or silly)
'one involved with insane rioting' is the wordplay.
'one' becomes 'i' (Roman numeral).
'involved with' means one lot of letters goes inside another (I've seen this in other clues).
'rioting' is an anagram indicator.
'insane' anagrammed gives 'asinne'.
'i' going within 'asinne' is 'ASININE'.
(Other definitions for asinine that I've seen before include "Extremely stupid or foolish" , "Absurd" , "Foolish, silly" , "Daft" , "Really silly, ridiculous" .)