The tempo of the clock signal produced is set by the loop length and the beats settings in the host tempo section.
In this version of the plug-in this functionality is tied to the 'Tap Record' feature. Essentially the clock is started and stopped by the end and beginning respectively of the recording. However using the three drop-down menus you can control exactly what MIDI messages are sent.
The 'Pause Clock' button lets you manually stop and resume the MIDI clock once it's running.
Please refer to this page for host compatibility information relevant to these features.