How to return arp to internal clock

Hello, I’m just getting started this week with the desktop and was experimenting with playing an external arpeggiator into the S6 when on a patch that uses the internal arp (e.g. factory A2). Once the S6 receives MIDI clock it syncs which is cool, but I can’t get back to internal arp clock so far without power cycling which seems extreme. Reading the manual I see the hint that S6 will automatically switch to MIDI clock receive, but I don’t see an explanation of how to turn it off. Any advice much appreciated!