As Turford mentioned, push brooms are easier to clean if they have removable heads. If you can take the block off, let it soak for about 30 minutes in a sink or small basin filled with soapy water. If the head doesn't detach, you can place it upright in a bathtub filled with soapy water instead. Once it's gotten soapy, you should rinse it off and allow it to air-dry.