If the track is truly stereo you should not make it mono as you will lose depth.
If the track is actually a mono or near mono sound but a stereo track the easiest thing to do is bring up 2 mono tracks and slide you stereo track down to the 2 mono tracks. Then you just delete the stereo track as well as one mono track and you are left with a single mono track.
I do this all the time with beats tracked out of Reason (since Reason bounces everything as stereo). I'll load everything into PT then mono down all the sounds that are truly mono.
Not sure this is what you were looking for, but there ya go.