To clear up a medical problem, infection, or disease means to cure it or get rid of it. If a medical problem clears up, it goes away. Antibiotics should be used to clear up the infection Acne often clears up after the first three months of pregnancy
To clear up a problem, misunderstanding, or mystery means to settle it or find a satisfactory explanation for it. During dinner the confusion was cleared up: they had mistaken me for Kenny. see also clear-up = sort out