If you are using the Grid Search filters from the app store, there is a Reset Button widget included with that package which will reset all of the filters. Just add it to your page and you are good to go.
If this is a custom search capability with a helper entity, you should be able to create a simple microflow that sets all of the attributes and/or associations on the search helper entity to empty and performs a search with no filters to refresh the list that is displayed. Should be just a few actions (Change the search helper entity setting everything to empty then call the search microflow that goes with your custom search capability). Once you create that, put it on your page and give it a whirl.
Hope that helps,
When the search bar is open you have next to the search button the clear search. Or am I missing your question here?
Screenshot of filters