Click the Filter Clips button at the bottom of the AceText Editor or AceText Tower, or press Ctrl+F3 on the keyboard, to display only clips containing the search term you've entered. The clips that don't contain the search term are not deleted. They're simply made invisible. Click the Filter Clips button again to make all clips visible again.
If you edit the search term while filtering clips, AceText will automatically re-apply the filter using the new search term.