Riddle got it locked in while standing and tripped Clements to the ground and into side control, where he immediately tightened it further and got the tap.
The official time of the victory was 2:02 of the third round.
The two had battled back and forth throughout, with Riddle showing his grappling superiority but Clements landing most of the fight's significant standup shots, with the exception of a first-round liver kick which referee Josh Rosenthal mistakenly believed was a low blow.
That blip aside, Riddle seemed as though he could take Clements down whenever he wanted, but chose to exchange with him for short bursts before going back to his bread and better.
"I made sure I banged a little, but I got back to my roots to get that 'W,'" he said.
It was the second straight win for Riddle, who is now 7-3.
In losing, Clements had a five-fight losing streak snapped. The defeat makes him 11-5.