Hmmm!

Ok, I'm no mechanic. My wife's car has a back wheel which binds, and often she has to reverse to release it. Now I'm having a go at it but, I am clueless as to what to do next. After a brush out and a quick blow with an air duster, I'm stuck. I suppose I could give it a squirt of oil but I don't think it would be a very good brake after that!