Bolt, lock (3)
I believe the answer is:
bar
I believe this clue is a double definition.
'bolt' is the first definition.
(thesaurus)
'lock' is the second definition.
(thesaurus)
(Other definitions for bar that I've seen before include "Sandbank; prohibit" , "Local" , "saving" , "Pub; block (access)" , "Obstruct" .)