Stop in the name of the law (6)
I believe the answer is:
arrest
'stop' is the definition.
(synonyms)
'in the name of the law' is the wordplay.
'in the' is an insertion indicator.
'name' becomes 'Art'.
'of the law' becomes 'res' (I am not sure about this - if you are sure you should believe this answer much more).
'art' enclosing 'res' is 'ARREST'.
Can you help me to learn more?
(Other definitions for arrest that I've seen before include "Land next to the sea" , "Stop - detain" , "Detain under suspicion of criminal behaviour" , "apprehend a law-breaker" , "Stop (on suspicion)" .)