I believe you're talking about custom clothes added by MoreClothing. Default clothing can't be removed but if you go into the moreclothingV15settings.txt, located in Mods/$INIT$, you can select clothes and accessories to remove from the game by placing ; to the left of them. You can also change the order they appear in game by rearranging them in the settings file.
But if you meant the default clothes that will show up if you run SDT without the Loader, there's no way to remove those as far as I know.