Discontinues punctuation marks (5)
I believe the answer is:
stops
This clue is a double definition.
'discontinues' is the first definition.
('stop' can be a synonym of 'discontinue')
'punctuation marks' is the second definition.
(stop is a kind of punctuation mark)
(Other definitions for stops that I've seen before include "Posts (anag.)" , "Discontinues" , "Checks" , "Halts" , "Prevents" .)