I want to remove audio from a video file/vlog in order to use it as a podcast.
However, as the video file is also my original vlog broadcast, I don't want any changes that I make to affect the vlog audio.
how can I do this in audition?
Open the file in Audition, and use Save As for the audio track - give it a different name. Audition can't alter the original; there is no facility for doing that, so your original file will remain intact.