West's leader becoming a calamity? (8)
I believe the answer is:
accident
'calamity?' is the definition.
(calamity is a kind of accident)
I don't understand the rest of the clue.
(Other definitions for accident that I've seen before include "Unexpected and unplanned event" , "Chance event with no apparent cause" , "Pile-up" , "Contretemps" , "Eg, car crash" .)