Stanch, check (4)
I believe the answer is:
stem
This clue is a double definition.
'stanch' is the first definition.
(I know that stanch can be written as stem)
'check' is the second definition.
(both can mean to control or stop)
(Other definitions for stem that I've seen before include "Ski turn and plant stalk" , "Thwart; support" , "Stalk - check" , "something growing?" , "Supporting structure" .)