His father, Kim Clackson, played in the National Hockey League (NHL) for the Pittsburgh Penguins and Quebec Nordiques.

Clackson attended Peters Township High School in McMurray, Pennsylvania, and played for the school's varsity ice hockey team, winning two Pennsylvania State AA Ice Hockey Championships.

[1] After high school, he played two seasons of Junior A with the Chicago Steel of the United States Hockey League (USHL) and was selected 215th overall in the 2005 NHL Entry Draft by the Philadelphia Flyers.

After his junior season, he decided to forgo his senior year by signing with the Flyers on March 19, 2008.

[2] On June 7, 2011, Clackson was packaged into a trade that sent him, a 2012 third round draft pick and future considerations, to the Phoenix Coyotes, in exchange for goaltender Ilya Bryzgalov.