Can I clear the event queue in my listener?

No, you cannot clear the event queue inside a listener. This is by design as a listener should not be able to stop the processing of the current event and should focus on interaction between the controller (Mach-II) and your model. If you need to clear the event queue inside a listener, you probably need to use a filter. Filters should focus on the interaction between the controller (Mach-II) and your event-handler.