Dramatic south of France hideaway (6)
I believe the answer is:
sudden
'dramatic' is the definition.
(thesaurus)
'south of france hideaway' is the wordplay.
'south of france' becomes 'sud' (French for south).
'hideaway' becomes 'den' ('den' can be a synonym of 'hideaway').
'sud'+'den'='SUDDEN'
(Other definitions for sudden that I've seen before include "'Unexpectedly, without warning (6)'" , "Quickly, without notice or warning" , "Quick and unexpected" , "Happening quickly and without warning" , "Immediate and surprising" .)