Check stalk of plant (4)
I believe the answer is:
stem
This clue is a double definition.
'check' is the first definition.
(both can mean to control or stop)
'stalk of plant' is the second definition.
(Other definitions for stem that I've seen before include "Type of cell" , "Block" , "Slender vertical part, glass or plant" , "Thwart; support" , "Staunch (flow)" .)