Clancy's journey began in Ottawa, where he developed his raw talent and fierce competitive spirit. From 1919 to 1937, his professional career saw him suit up for several teams, including the Ottawa Senators and Toronto St. Pats (later Maple Leafs). Clancy became a tenacious defenseman throughout his playing days, earning the nickname "King" for his leadership on and off the ice. He aided the Senator's Stanley Cup wins in 1921 and 1922 and was a crucial figure in the Leaf's Stanley Cup win 1932.

Beyond his accomplishments, Clancy's true impact lies in his unwavering influence on the game. He was a vocal advocate for player safety, pushing for rule changes to protect players from dangerous on-ice tactics. Additionally, his leadership extended beyond the rink. He served as the first president of the National Hockey League Players' Association (NHLPA), championing the rights and well-being of his fellow players.

Following his playing career, Clancy transitioned seamlessly into coaching and executive roles. He served as head coach for the Toronto Maple Leafs and the Montreal Canadiens, leading the Canadiens to another Stanley Cup victory in 1946. As general manager, he continued to be a driving force in the sport, shaping the Maple Leafs organization for several years.

King Clancy's legacy rests not solely on his hockey prowess but on his unwavering commitment to the sport.