What will clear diaper rash?

Depends. If it is an irritant diaper rash, involving buttocks, thighs, and not the skin crease, then desitin, (zinc oxide diaper cream) a7d, balmex, etc. If it involves the skin creases, spares the bum, and there are some red dots involving the area above the genitas, then it maybe a yeast infection.And lamisil, or lotromin will help.
Keep area dry. Moisture, heat and lack of air circulation may cause skin irritation which may get over infected with bacteria or fungus. Baby may need a medicated cream, so if no improvement with careful drying and vaseline/zinc oxide based ointments, see a doctor.
Diaper rash. For diaper rash keep baby's skin clean & dry. Change diaper as soon as it's soiled or wet. For healing allow baby to go without diaper for periods of time so affected area can air out. Avoid tight diapers or airtight covers over diaper. Meds your Dr. might recommend include antifungal cream (for fungus), a steroid cream (for significant inflammation) or an antibiotic (for bacterial infection.)