Shielding the ball is one way to keep possession of the ball. It happens all over the field in many different situations. And ideally only happens for a few seconds until you find a teammate you can pass the ball to. But when it happens, it usually happens on the sidelines , closer to the side of the field. There are different ways to shielding the ball. One way is with the back to the defender. The more recommended way to shield the ball is actually being positioned sideways, having the ball on the outside having the opponent on the other side. This way you are able to see whats going on at least on one side of the field, this way you have a chance to keep the opponent further away from the ball, to not be able to reach it. Kick it away. And the other thing is you are able to make a move yourself.
Nobody is coming in, you have a chance to direct your opponent. You have a chance to actually be more active and lead and guide the opponent the wrong way to then create some space for yourself to get out of this pressure situation. Keep in mind that you wanna use your upper body. Lean in a little bit to your defender. Don't have the ball with the foot on the ball. Instead keep the ball moving slowly, but constantly so you have a chance to react on eventual attacks from your opponent. But should not take longer than 30 seconds or 3 seconds or 5 seconds. Just make sure you are in a ready position . Lead the defender in the wrong direction, and get open as quickly as possible to free yourself and continue with the game. That's the basic idea of shielding.