To clear a blocked drain, start by using a plunger to try and dislodge the blockage. If that doesn’t work, use a drain snake or auger to break up the obstruction. Another option is to pour boiling water down the drain, followed by a mixture of baking soda and vinegar. Let the mixture sit for a few minutes before flushing with hot water. Avoid using harsh chemicals as they can damage pipes and harm the environment. If the blockage persists, it may be best to call a licensed plumber to assess and fix the issue. Plumbers will be able assess the drain to ensure its not a bigger problem like tree roots or broken pipes.