a clean sheet
1. (mainly British) if you are given a clean sheet, you can start something again, and all the problems caused by you or other people in the past will be forgotten I want us to forget all the arguing of the past, and start the New Year with a clean sheet.
2. (British) if a football team or a goalkeeper (= the player who stands in the goal) has a clean sheet, they do not allow the other team to score any goals United kept a clean sheet in an away match for the first time this season.