Essentially a clear is a high powered shot that the player hits from one end of the court all the way to the other end of the court. The purpose is to hit the shuttle as high as possible, perhaps arching the ceiling. I'm going to demonstrate very slowly just how to go about doing a clear swing.
I'm going to start off facing the net. And then you turn your shoulders perhaps 180 degrees and then you start the rotation and the swing. And you typically hit the shuttle when it's directly overhead you and perhaps a little bit in front of you and you make contact. And when you make contact you want to end with a rotation of your elbow and finally end somewhere around here.
Now, notice when Chuben hits the forehand clear, he's turning his shoulders which gives you perfect range of motion and you're able to generate most power that way. And he's striking the shuttle when it's either above his head or slightly in front of him. It's very important to get behind the shuttle to hit an effective clear.
Again, timing is very important. Timing is important so that you hit the shuttle right in the center of the racquet and you hit it flat. So you get maximum power and control.
And that's basically how you do the overhead clear.