A grave is disturbed causing unexpected changes (8)
I believe the answer is:
vagaries
'unexpected changes' is the definition.
(vagary means an unexpected or eccentric change)
'a grave is disturbed' is the wordplay.
'disturbed' indicates an anagram.
'a'+'grave'+'is'='agraveis'
'agraveis' is an anagram of 'VAGARIES'.
'causing' acts as a link.
(Other definitions for vagaries that I've seen before include "changes that cannot be forecast" , "Capricious acts or ideas" , "Unpredictable occurrences" , "uncertainties" , "Whims" .)