Calamity -- can't dice bananas (8)
I believe the answer is:
accident
'calamity' is the definition.
(I've seen this before)
'can't dice bananas' is the wordplay.
'bananas' is an anagram indicator (informal term for mad).
'cant'+'dice'='cantdice'
'cantdice' anagrammed gives 'ACCIDENT'.
(Other definitions for accident that I've seen before include "disaster" , "Unforeseen mishap" , "Unforseen misfortune" , "Dance tic leading to mishap" , "Unexpected and unplanned event" .)