A tough and physical defenceman, Cleghorn had a reputation for violent play; he was twice charged with assault following on-ice incidents and was subject to efforts to have him banned from the NHL.

At the time of his retirement, Cleghorn's 169 career goals were second most in professional hockey history by a defenceman, behind Harry Cameron's 173.

In the 1909–10 season, he played for the New York Wanderers of the American Amateur Hockey League and scored seven goals in eight games from the center forward position.

[3][6] Cleghorn would often retaliate violently against opposing players he felt were taking liberties on his teammates, especially his brother Odie.

[7] In a January 1917 game against the Toronto Blueshirts, Cleghorn collided with Ken Randall and crashed feet first into the boards.

While recovering from his injury later in 1917, Cleghorn suffered another fall while walking an icy street in Montreal and fractured his other ankle.

The Senators asked that he be allowed to return to their team, for which George Kennedy, owner of the Montreal Canadiens, threatened to have Ottawa thrown out of the league.

[11][12] Cleghorn eventually signed with the Toronto St. Patricks, playing with them for the regular season in which the team won the NHL's second half championship.

Just before the start of the 1921–22 NHL season, Hamilton traded him to the Montreal Canadiens for Harry Mummery and Amos Arbour.

[6] In another incident with the Senators in 1922, he initiated a brawl during which he injured three players, Eddie Gerard, Frank Nighbor and Cy Denneny.

[18] During his time in Boston, he served as a veteran presence on the team and as a mentor to future Hall of Fame defenceman Eddie Shore.

[22] That season, the Maroons racked up 19 wins and 22 losses, finished third in the Canadian Division and made the Stanley Cup playoffs.

Cleghorn was hired in 1935 by the Pittsburgh Shamrocks of the International Hockey League (IHL), but was fired by the team near the end of the season over a dispute with club president Ray Babcock over the payment of his salary.

[26][27] Known for both his intense competitive nature and violent temper, Cleghorn was considered one of the toughest and dirtiest players of his time.

[28] Respected by his teammates and hated by his opponents, Cleghorn often used his stick as a weapon and was routinely among his team's leaders in both goals and penalty minutes.

[28] In the season when Ottawa unsuccessfully attempted to have him banned from the NHL, Cleghorn led the league in penalty minutes with 80.

[6] His ability to rush the puck forward also made him a scoring threat; Cleghorn was one of hockey's first offensive defencemen.

"[2] Two days later, Odie died in his sleep of heart failure and was found by his sister just hours before Sprague's funeral.