After the defense makes a stop and regains possession of the ball its time to run the clear.
In lacrosse, clearing means to get the ball from the defense to the offense. An ideal clear leads to a fast break scoring chance against the opponent and there are many reasons most clears can be relatively automatic. You and your team will soon notice if you are making failed clears, however, in the intangibles of momentum and morale, and also practically, because without successful clears you will be playing a lot of defense and will not have the ball in position to attack the opponent's goal and score.
An unsettled clear is when the the defense, often the goalie, gets the ball in the course of live play and the team has to get it up field.
A settled clear is when the ball changes possession to a team on their defensive half of the field after a stoppage in play, maybe picked up on the end line after a shot or the sideline after going out of bounds. The main difference with settled clears in lacrosse is that the clear can not begin until the referee blows the whistle to resume play.