Great disturbance (8)
'great disturbance' is the definition.
This is the entire clue.
(Other definitions for upheaval that I've seen before include "Major disturbance" , "State of violent disturbance and disorder" , "At university, books are taken in to cure" , "Violent or sudden disturbance" , "Disorder, turmoil" .)
'great disturbance' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for turmoil that I've seen before include "State of great disturbance or confusion" , "Hubbub" , "agitating activity" , "Violent commotion" , "Unrest - upheaval" .)