The term ALI, ONCE is a reference to the late Muhammad Ali, who was a professional boxer and three-time World Heavyweight Champion. The crossword solutions for this term are CLAY (4 letters) and CHAMP (5 letters). CLAY is a reference to Ali's birth name, Cassius CLAY, which he changed after converting to Islam in 1964. CHAMP is a reference to his nickname, 'The Greatest', which was given to him by sportswriters after his win against Sonny Liston in 1964.