You can archive your screener but cannot delete it completely. To do this, go to your screener dashboard (Screeners>>Overview), hover over the blue quick edits icon, and click "archive." This will remove that particular screener from the screener overview. You can always bring back an archived screener by clicking on "Restore Archived Screeners" and selecting the screener that you want unarchived.
If you are archiving a screener, be sure to take the ethnio code off of any sites! Otherwise you'll still be incurring pageviews.
Note: for links, if you archive a screener it will automatically turn the screener off. So be sure your project is completely finished before deleting/archiving.