Drastic split ending in divorce (6)
I believe the answer is:
severe
'drastic' is the definition.
(I've seen this before)
'split ending in divorce' is the wordplay.
'split' becomes 'sever' (I've seen this before).
'ending in' indicates one should take the final letters.
The final letter of 'divorce' is 'e'.
'sever'+'e'='SEVERE'
(Other definitions for severe that I've seen before include "Ascetic - demanding - bitter" , "Taxing" , "Terrible" , "Austere, harsh (6)" , "Arduous - dangerous" .)