Imprison or confine (4,2)
I believe the answer is:
lock up
I believe this is a double definition.
'imprison' is the first definition.
(thesaurus)
'confine' is the second definition.
(I know that lock up is a more specific form of the action confine)
(Other definitions for lock up that I've seen before include "Jail; type of garage" , "Secure garage" , "Immure" , "Shop without living quarters" , "Cell for prisoners" .)