I have a white cat, who loves to be outside for short amounts of time. It is during her outside visits that she loves to roll in dirt. Either she can't reach her back for bathing (she's avg. size) or she just doesn't want to. In any case, she has developed a large clump of fur on her back which I cannot brush out and she tries biting if I try to cut it off. Is there any advice out there for this kind of problem?