The best way to get rid of a sand cloud is to prevent it from happening in the first place by washing your sand thoroughly to remove all debris before adding it to your tank.
Once you have a sand cloud, you will need to wait until the sand cloud settles which may take as long as 7 days. There are a few tips you should know that will help the sand cloud to settle faster.
Do not run the filter as the sand in the water will damage it.
Do not move your tank, this will agitate the sand and make the sand cloud worse.
Do not add anything to your tank until the sand cloud settles as this will simply agitate the sand. The sand cloud will take longer to settle after the sand has been agitated.
Change the water daily. Each time you change half the water, the time that the sand cloud will last is reduced.