Disallow the final scourge (4)
I believe the answer is:
bane
'scourge' is the definition.
('bane' can be a synonym of 'scourge')
'disallow the final' is the wordplay.
'disallow' becomes 'ban' (banning is a kind of disallowing**).
'final' suggests the final letters.
The final letter of 'the' is 'e'.
'ban'+'e'='BANE'
(Other definitions for bane that I've seen before include "Cause of great distress, rhymes with rule" , "scourge" , "Blight" , "Cause of trouble or anxiety" , "A fatal poison" .)