Split the rent (4)
I believe the answer is:
tear
This clue is a double definition.
'split' is the first definition.
(I know that split can be written as tear)
'the rent' is the second definition.
('tear' can be a synonym of 'rent')
(Other definitions for tear that I've seen before include "Secretion of the lachrymal glands" , "speed" , "Lachrymal fluid" , "Drop secreted by the lacrimal glands" , "Droplet; rip" .)