The crossword solution for the term CLAY, SINCE 1964 is ALI, which stands for Muhammad Ali, the legendary American boxer. Ali was a three-time World Heavyweight Champion and is widely considered one of the greatest boxers of all time. He began his professional career in 1964 and was known for his unique style of boxing, which he called 'float like a butterfly, sting like a bee'. Ali was also an outspoken civil rights activist and was awarded the Presidential Medal of Freedom in 2005.