You don't want to clear it, it will immediately start to fill again anyway. It keeps a small cache, continually replacing the oldest event with the newest. Most devices the cache is 200KB, and there is no way to prevent it from tracking. Shrink will remove the viewer, but it will still be operating in the background.
That will access it, and you can clear it by hitting the menu button once it's open, but there still is no point to clearing it. Especially if you have a problem. It's one of the best resources you have to detecting the source.