Remove unwanted plants (4)
I believe the answer is:
weed
'remove unwanted plants' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for weed that I've seen before include "Cannabis; feeble person" , "Plant growing where it is not wanted" , "Got rid of water" , "Plant growing in the wrong place!" , "Uncultivated plant" .)