Record without guests. Then in your favorite audio editing program: You could try the old inverse isolation for centered audio if the original live recording is a stereo pair which could theoretically give you a cleaner mono audio track but results will still be less than ideal. There are also plugins or VSTs to remove reverb but a truly good one will be $$$. And again, results will likely be "fair" to "terrible". Last ditch effort could be good old EQing or some combination of all the above with the additions of a noise gate plugin. Best of luck.