If a podcast episode is hosted by a guest host, how do I include the regular host’s name in my work-cited-list entry?

You should not include the regular host’s name in the work-cited-list entry. Include the guest host’s name in the “Author” slot of the entry, since that is the host of the particular episode you are citing:

Bianculli, David, host. “Margo Price.” Fresh AirPodcasts app, 31 Jan. 2019.

See our post on citing a podcast episode.