We actually have a couple different ways to clear the results to a poll question. If you are in Google Slides > when you’re in Presentation mode > on the right side of the page there are some grey control buttons > you can use these to clear the results one at a time.
Otherwise, you can clear your polls in bulk from our website at polleverywhere.com/my/polls – you can see some details for how to do this here: https://www.polleverywhere.com/guides/presenter/getting-started#clearing-responses
Those options are available now. We do plan on creating a more full Edit experience within Google Slides. But, that is still a few months out at least for us