Radical change (8)

I believe the answer is:
upheaval
'radical change' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for upheaval that I've seen before include "At university, books are taken in to cure" , "Violent or sudden change or disruption" , "Great disruptive change" , "Turbulence" , "Disruptive disturbance" .)