Before you do that, try putting a thin strip of cloth tape on the handle underneath where the clip is. That should add some friction to the handle without putting it in to "pants-shredding" territory. I do that with a couple of my folders using hockey stick tape (you can get it at any sporting supply store).
For a more permanent change, you could mask off the area underneath the clip and roughen it up with some 80 grit sandpaper.