Disruption (8)
'disruption' is the definition.
(I know that upheaval is a type of disruption)
This is the entire clue.
(Other definitions for upheaval that I've seen before include "Disruptive disturbance" , "At university, books are taken in to cure" , "Disorder, turmoil" , "Violent or sudden change or disruption" , "Turbulence" .)
(Other definitions for unrest that I've seen before include "State of agitation" , "Disturbance or dissatisfaction" , "revolutionary state" , "'Disturbance, agitation (6)'" , "State of uneasiness" .)