Ruler exercises right during more rioting (7)
I believe the answer is:
emperor
'ruler' is the definition.
(emperor is a kind of ruler)
'exercises right during more rioting' is the wordplay.
'exercises' becomes 'pe' (Physical Education class).
'right' becomes 'r' (common abbreviation).
'during' is an insertion indicator.
'rioting' is an anagram indicator.
'pe'+'r'='per'
'more' is an anagram of 'emor'.
'per' going within 'emor' is 'EMPEROR'.
(Other definitions for emperor that I've seen before include "Tsar" , "Monarch" , "Napoleon Bonaparte, for instance" , "Beethoven piano concerto, Op. 73" , "Eg, Caesar" .)