Hello Inderjeet, deselectAll() method is useful to remove selection from all selected options of select box. It will works with multiple select box when you need to remove all selections. Though it clears all selected entries, but it is only valid when the SELECT supports multiple selections. Syntax for deselectAll() method:
Select listbox = new Select(driver.findElement(By.xpath("//select[@name='FromLB']")));
listbox.deselectAll();