In his
freshman year at the
University of California, Los Angeles, in
2020–21, Clark was a
reserve and averaged 2.5 points and 2.4 rebounds in nine minutes per game for the
Bruins. He made the game-winning
free throw in an 80–79 win over
Arizona State at home in
Pauley Pavilion. In the
2021 NCAA tournament, UCLA unexpectedly advanced to the
Final Four. He had a season-high nine rebounds in 18 minutes in an overtime victory over second-seeded
Alabama in the
Sweet Sixteen. He averaged 6.7 points and 3.8 rebounds in 18.1 minutes per game. In the nine games in which he played 20 or more minutes, Clark averaged 11.4 points and 5.6 rebounds. In February, during a three-game span versus
Washington State,
Washington, and Arizona State, he averaged 19.7 points, making 3 of 8 on
3-pointers, and added 8.3 rebounds and 2.7
steals. In the Bruins' season opener, he scored 17 points on 7-of-7 shooting and had seven steals in a win over
Sacramento State. In the regular season finale against
Arizona, he suffered a right
Achilles tendon rupture and was ruled out for the
2023 Pac-12 tournament. The top-seeded Bruins advanced to the tournament finals, before losing 61–59 to No. 2-seed Arizona. UCLA, who was vying for a No. 1 seed in the
2023 NCAA tournament, He underwent surgery three days after the injury. Clark averaged 2.6 steals per game during the season, which led the Pac-12 and ranked fourth in the nation. he won the
Naismith Defensive Player of the Year Award, and the
National Association of Basketball Coaches named him
their defensive player of the year. Voted the
Pac-12 Defensive Player of the Year, Clark significantly improved on offense and became UCLA's second-leading scorer. After the season, he
declared for the NBA draft. The timetable for his recovery was estimated to be 8–10 months. ==Professional career==