You can clean the wicks by rinsing them under some really hot water, or even soaking them in water, PGA, or vodka. A dry burn usually follows this step, although any time I attempted to dry burn a normal commercial clearo it never worked the way it was supposed to.
Your surest bet it to just swap out the wicks for new ones, but if that isn't an option, hot water rinse. Make sure it's air dry before you vape it.