Violent upheaval or disaster (9)
I believe the answer is:
cataclysm
I believe this clue is a double definition.
'violent upheaval' is the first definition.
(I've seen this before)
'disaster' is the second definition.
(synonyms)
(Other definitions for cataclysm that I've seen before include "Calamity" , "Debacle" , "Sudden violent change in the earth's surface" , "Violent event" , "Deluge: upheaval" .)