My kitty has been sleeping under the couch lately and I think got some kind of grease on her back where she can't reach.. There are two large clumps of fur at the bottom of her back not far from her tail. Is there some way to clean this, or should I just snip off the clump of fur? OTOH, she is overweight and I'm wondering if that is contributing to this new problem. Thanks very much for any advice.