FLIP THE SHIRT
We use the term "flip the shirt" when we are coaching up olympic lifts like cleans, and snatches. What I mean by this is that when your shirt is untucked and you perform a clean or snatch the bar should stay close to your body that it will flip the bottom of your shirt. Now, I'm not saying to try to make sure your shirt flip up everytime. But just having that cue in your mind will make sure you keep the bar close to your body keeping the center of gravity close to you.
When the bar travels away from your body the center of gravity moves which will make your upper body lean forward. If you ever perform a clean and when you come to the rack position, with bar on your shoulders, and you are a slightly falling forward that is a good sign that the bar travelled away from your body. Remember "flip the shirt".