Spoiler! You can clear out your entire guest list at once via the righthand side of the Guest List section of the webapp.
Often times when testing the RSVP form, hosts will add fictitious guests and submit test RSVPs. Other times, people realize they made a mistake during the import process and would just rather start over. Either way, hosts can delete their entire guest list via the Guest List section of the web application:
Tags: Delete guest list, clear guest list, start over on guest list