That will get you a new instance of the same type of object as the first, but it won't preserve any state, such as graphics drawn with the drawing API, or alpha, or children.

If you just want to clone the appearance of a movieclip, you can draw it into a bitmapdata using the draw method, then use that bitmapdata to create a Bitmap, or as many Bitmaps as you want. This of course also won't preserve any actual state, just appearance. And I don't think it'll preserve filter effects.