Riot generated by bread (4)
I believe the answer is:
roti
'bread' is the definition.
(roti is a type of bread)
'riot generated' is the wordplay.
'generated' is an anagram indicator.
'riot' is an anagram of 'ROTI'.
'by' acts as a link.
(Other definitions for roti that I've seen before include "Indian flatbread" , "Indian bread (not naan)" , "spicy sandwich" , "Indian flat round bread" , "Indian bread cooked on a griddle" .)