System allowing force to arrest most senior officer (7)
I believe the answer is:
process
'system' is the definition.
(thesaurus)
'force to arrest most senior officer' is the wordplay.
'force' becomes 'press' (both can mean to coerce).
'to arrest' indicates putting letters inside (arrest can mean capture).
'most senior officer' becomes 'oc' (I can't explain this - if you can you should believe this answer much more).
'press' placed around 'oc' is 'PROCESS'.
'allowing' is the link.
Can you help me to learn more?
(Other definitions for process that I've seen before include "Course of action intended to achieve a result" , "Deal with in a routine way" , "Series of steps achieving a particular end" , "Use IT perhaps < to handle" , "Corpses in series of steps" .)