The arm drag is a great technique you can use to get to your opponent's back from the clinch. It's shown below from the low tie up, but can also be used from a variety of other positions.
From the low tie up, you might consider kneeing your opponent in the groin to loosen him up before the arm drag.
Keeping your opponent's arm secure, grab his wrist and use the weight of your body to shove it down in front of you.
Using the hand on his triceps, yank his arm past you, giving you access to your opponent's back. There are many options here, from control positions and take downs to chokes and face pulls.
Back to the clinch.