clean slate

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun nautical a slate on which the courses steered by a ship (and distances run) were recorded, but have been wiped clean after being entered in the log at the end of a watch
• noun by extension a fresh start

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an opportunity to start over without prejudice