This is what "What HI-FI" has to say about your question in a section of their web site re: system maintenance...
...CD player lenses can also get dirty, especially in smoky or dusty environments. If your player starts to skip, you can try a cleaning disc - these usually have little brushes on them to sweep the lens clean, and are sometimes used in conjunction with a drop of cleaning fluid provided. They usually do the trick - if not, older players may need to go to a repairer to be opened up for a clean.
...CD player lenses can also get dirty, especially in smoky or dusty environments. If your player starts to skip, you can try a cleaning disc - these usually have little brushes on them to sweep the lens clean, and are sometimes used in conjunction with a drop of cleaning fluid provided. They usually do the trick - if not, older players may need to go to a repairer to be opened up for a clean.