[6][7][8] On July 23, 2021, Clarke was selected in the first-round, eighth overall, by the Los Angeles Kings in the 2021 NHL Entry Draft.

[13] Clarke collected his first career NHL point, an assist, during a road game against the Pittsburgh Penguins on October 20, 2022, making Clarke the seventh youngest defenceman and 18th youngest player in Kings history to record a point.

[14] When in Los Angeles, Clarke – then the NHL's second-youngest defenseman during the 2022–23 season – billeted at the home of Jonathan Quick, the Kings' goaltender and oldest player at that time.

[23] He finished the regular season with 10 goals and 36 assists in 50 games, and was named to both the All-Rookie and Second All-Star Teams.

[25] Clarke won Gold playing for Team Canada in the 2021 IIHF World U18 Championships, averaging a point-per-game.

[32][33] On December 12, 2022, Clarke was named to Team Canada to compete at the 2023 World Junior Ice Hockey Championships.