Unless I'm missing something, the way you clear filters is to close the relevant filter pane and (re)execute a search from the Quick Search box.
But the drift I'm getting is that many users will conduct "filter-only" searches - they'll just drill down in the filters with no underlying search.
So, it might be worthwhile to have a clear function somewhere in the Filters tab, or maybe pane by pane.
Now, I suppose, technically, one has to have a search in the search box, even if it's just "". Which, now that I think about it, suggests that "" should maybe be available as a button or something. "View Entire Catalog" or some such.
