Grasslike plant of wet places (5)
I believe the answer is:
sedge
'grasslike plant of wet places' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sedge that I've seen before include "Herons" , "plant with triangular stems" , "Bog plant; type of warbler" , "Plant growing in swampy ground" , "Wetland grass-like plant" .)