2007-08: Adam Clendening played for the Toronto Marlboros Midget AAA club, scoring 8 goals and adding 42 assists for 50 points while compiling 116 penalty minutes.
2008-09: Clendening split time between the U.S. NTDP U-17 and U-18 squads. In 39 games for the U-17 team, Clendening scored 1 goal and added 13 assists for 14 points. In 23 games for the U-18 team, Clendening scored 1 goal and added 4 assists for 5 points. Clendening played for the USA's gold medal squad at the 2009 U-18 World Junior Championship, picking up 2 assists in 7 games.
2009-10: Clendening split time between the U.S. NTDP U-18 national squad and the team that competed in the USHL. In 65 games for the U-18 team, Clendening scored 14 goals and added 35 assists for 49 points to go along with 120 penalty minutes. In 26 games for the USHL squad, Clendening scored 4 goals and added 13 assists for 17 points to go along with 44 penalty minutes. Played for the USA's gold medal squad at the 2010 U-18 World Junior Championship, scoring 3 goals and adding 7 assists for 10 points in 7 games. He was named to the tournament All-Star Team for his efforts.
2010-11: In his freshman season at Boston University, Clendening played in 39 games for the Terriers. He scored 5 goals and added 21 assists for 26 points to go along with 80 penalty minutes. Clendening was named to Hockey East All-Rookie Team.
2011-12: Clendening was the leading scorer among defensemen for Boston University as a sophomore and represented the USA at the 2012 U20 World Junior Championship along with fellow Blackhawks prospect Stephen Johns. In 38 games for the Terriers he scored 4 goals with 29 assists and was plus-11 with 64 penalty minutes. After finishing tied for second in Hockey East the Terriers lost to Maine in the Hockey East tournament semifinals. Boston University received an at-large bid to the NCAA tournament; falling to Minnesota in the West Regional semifinals. In six games at the WJC, Clendening scored 1 goal with 4 assists and had 6 penalty minutes on a USA team that finished seventh in the ten-team tournament. In June 2012 he signed a three-year entry-level contract with the Blackhawks; foregoing his final two years of college hockey.
Clendening is an offensive defenseman blessed with superb puck-moving ability and on-ice vision. His excellent puck skills are one reason why many scouts are so high on Clendening. He can see plays develop and follows them quite well. He can also be found frequently jumping into plays too. Clendening's ability to move the puck and patience with it makes him an ideal quarterback on the power play. He makes very good decisions with the puck and distributes the puck very well. Clendening can also control the tempo of the game from the blue line. He is an excellent skater with good speed that can keep up with many of the faster opposing forwards. He also transitions quite well too. One area where Clendening will need to improve is keeping his feet moving more consistently. While he is known for his offensive prowess, Clendening is also solid defensively. He doesn't shy away from the physical side of the game and plays with a good deal of intensity. However, Clendening could stand to utilize his intensity and grit more to the benefit of his team. He possesses a very good shot and can get pucks to the net. As his rookie season at Boston University went along, one area that Clendening showed noticeable improvement in was the quality of shots he was taking.
Clendening is turning pro in 2012-13 following two prolific seasons at Boston University. The IceHogs are short on offensive-defensemen, which should give Clendening an opportunity to jump right into a significant role on the power play.