Double Olympic boxing champion Claressa Shields will make her mixed martial arts debut with the Professional Fighters League (PFL) in June when she faces Brittney Elkin, organisers said on Wednesday. American Shields, the first undisputed boxing world champion in two different divisions in the four-belt era, signed with PFL in December with the goal of becoming the “greatest two-sport athlete of all time”. PFL presents MMA in a format where individuals compete in a regular season, playoffs, and championship for a million-dollar prize,