Possible Clues:

• Period of low rainfall
• A medical attendant has a duty to ensure dryness
• December, except the middle, should get a dry spell
• Doctor should prescribe no water
• The doctor should need more water with it
• Prolonged spell of dry weather
• That medicine-man should dry up
• The doctor should take a drink if that's the trouble
• Shortage the debtor has a duty to make up
• Almost rainless? Nothing much more than that