Drop in rent (4)
I believe the answer is:
tear
I believe this clue is a double definition.
'drop' is the first definition.
(teardrop)
'rent' is the second definition.
(I know that rent can be written as tear)
'in' acts as a link.
(Other definitions for tear that I've seen before include "Drop secreted by the lacrimal glands" , "Rip, sever roughly" , "Lacerate - sign of sorrow" , "Rip the eye moistener?" , "Rip - drop from eye" .)