How to use the clear buttom

I am trying to code in the clear button and I am having problems! Can someone help me code in the button to the following code?

edit: I found the answer!!!

please, don't delete your code after you found a solution. Other people may face a similar problem...

...if you found the answer it would be nice if you would post it. So ohters could profit from it even if they search the forum at a later time.