Welcome to the forums.
Any time you use a power grinder on hardened and tempered steel, you run the risk of heating it too much and ruining the temper. That's not to say it cant be done. If you are not versed with grinders, a file would probably be your best bet, but progress would be s l o w. My suggestion would be to just use the knife and not worry about sharpening the clip. It's a great knife, and maybe my favorite Becker.