Civil disturbance (6)
'civil disturbance' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for riot that I've seen before include "Uprising" , "Take to the streets" , "Disturbance by unruly mob" , "Rampage" , "A wild public affray" .)
(Other definitions for unrest that I've seen before include "Discontent verging on insurrection" , "Turmoil, disquiet" , "Feeling of anxiety or turmoil" , "State of agitation" , "Troubled, rebellious, condition" .)