Head of AC-12 arresting Detective Sergeant etc (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

An insertion of DS in A NOON. A is ‘head of AC’ and ’12’ gives you ‘noon’. The insertion indicator is ‘arresting’ and the surface is a clever reference to the popular drama Line of Duty , where AC-12 was Anti-Corruption Unit 12.