Check (4)
'check' is the definition.
(both can mean to control or stop)
This is the entire clue.
(Other definitions for stem that I've seen before include "something growing?" , "supporter of tobacco?" , "Staunch - support" , "part of a ship" , "Supporting structure" .)
'check' is the definition.
(as in testing or checking something works)
This is the entire clue.
(Other definitions for test that I've seen before include "Trial - big match" , "Trial; Hampshire river" , "Sample" , "Check" , "Critical examination or trial of qualities or abilities" .)
'check' is the definition.
(both can mean to control or limit)
This is all the clue.
(Other definitions for rein that I've seen before include "Hold back" , "Restraining lead" , "Part of a horses's harness" , "(Horse's) guiding strap" , "Leather used for control in horse-riding" .)
'check' is the definition.
(both can mean to limit or control)
This is all the clue.
(Other definitions for curb that I've seen before include "Bridle" , "[LIMITATION]" , "Rein in" , "Constrain" , "Check or restrain" .)
'check' is the definition.
(I know that check can be written as bridle)
This is the entire clue.
(Other definitions for bridle that I've seen before include "Take offence" , "Restrain" , "Rein" , "Part of horse's headgear" , "Bristle" .)