I know some of my external sequencers are sending MIDI clock all the time, regardless of whether it is running or not.
You could try a CapyTalk switch. There's many ways to do this in Kyma but here is one approach that extracts the !BPM from the MIDI Clock :
(!Osc_clockStart setReset: !Osc_clockStop)
(!TimingClock durationBetweenTriggers: 24) s bpm removeUnits