The underhook throw from the clinch is one of those techniques that looks complicated but really comes down to one thing: passing the leg to create a better angle of attack.
Here's what happens. Your opponent throws a round kick. You catch it. And most guys just grab the leg and try to muscle the sweep from right there. If you're shorter or don't have great wrestling, that almost never works.
The fix is simple. After the catch, you pass the leg through -- pull it across your body like an arm drag. That repositions you at an angle where the sweep becomes almost effortless.
Catch. Pass. Sweep.
The actual sweep mechanics matter too. You want to target directly under the calf, right at the Achilles. Not behind the knee -- legs are too strong there. And not on the thigh -- too much mass. Get underneath the calf with an upward lifting motion as you sweep through.
Think of it as a windshield wiper across the chest with your arm as you attack the base leg. All their weight is on that one leg, so when you hit the right spot with the right angle, they're going down hard.
One thing people skip: drilling both sides. You have to be able to catch and dump from the switch kick too. Same mechanics, opposite side. Catch, pass, sweep.
For the full clinch fighting system including throws, trips, and dirty boxing setups, check out our complete dirty boxing guide. The entire course is available in the Complete MMA Fighting System.