Maximize your browser window and use theater mode (third icon from right) to make the clip as wide, without actually making it fullscreen. There's also some shortcut keys explained in the YouTube help, but they are not available for every player type (being that some require Flash and don't work with the HTML5 players). Do some digging via Google and you're sure to find it. You can also try to copy&paste the video URL and then append the various player options to view it without a control bar. that's also explained in the YT help.
Mylenium