Hurry up. Go faster. Suggests one is taking too much time to accomplish a task.  ‘Lead’ is used as a heavy weight of metal that is slowing you down, so get it out and speed up. Often used by a boss to  his workers or a coach to his players. (Compare to Shake a leg, On the double or Get moving.)

“Can you kids hurry and get the lead out or we’ll be late  to the movie.”