Here is a small snack of a plugin a mono gate.
Alleygate is a mono gate. It uses the left & right input channels – one is input signal, one is gate signal. When the gate signal drops below zero the input signal will be entirely muted. In this respect it is has two states: on or off.
Setup should be easy: pan one signal one way, the other another way. Send them both to the plugin. You can adjust which channel is the gate signal alongside dry/wet in the plugin parameters.