We have a video explaining this self defense move, of how to get out of a single handed, standard shirt grab:
With a single handed shirt grab, the intent is to display dominance. It can also be to control and restrict the movements of the victim. It is imperative to know how to escape this situation with the correct martial arts movements.
I've broken this down into 3 steps:
1. Create the Opening
2. Back Foot Thru, Turn Around, Butt Out, Head Out
3. The Crank
After you understand the basic steps, try connecting them in a fluid manner, but slowly. Once you become more comfortable with that, take it a little faster.
This movement has more of its philosophy roots in Jiu Jitsu, where the purpose and objective is to blend with the attacker's energy, and utilizing leverage and timing as a way to neutralize and counter the attack.
But it is the forward intent of Kung-Fu that you need to commit fully to the move, and make it flow seamlessly, literally turning 3 steps into 1.
See the video here: https://youtu.be/ZN2vbZfz5rc