This is a simple little extension that has one purpose in life. Have you ever clicked a link on a web page, and then cursed yourself because you had meant to open it in a new tab? Dealing with that little error is a hassle: you have to click the Back button, find the link and click it again, this time remembering to hold down the command key.
But with Clone & Back installed, all you have to do is click its toolbar button, and the extension will do the rest for you. It will clone the current tab to a new one, and then go back to the previous page.