Have it inspected immediately at a tire and alignment shop. Clunks are never something to ignore, and Fords have more trouble with steering and suspension parts separating and leading to loss of control and crashes than all other brands combined. They will start with the ball joints and tire rod ends. Worn control arm bushings can make noise too and lubricating them won't fix that. Anti-sway bar links will rattle too but those are not a safety hazard.