Stop support for plant (4)
I believe the answer is:
stem
I believe this is a double definition.
'stop' is the first definition.
(I know that stem is a more specific form of the action check)
'support for plant' is the second definition.
(a stem holds a plant up)
(Other definitions for stem that I've seen before include "Stalk; restrict (a flow)" , "part of a ship" , "Ski turn and plant stalk" , "Axis" , "Upward part of a plant" .)