A car that clunks when going over bumps is usually caused by something with the suspension.
A joint in the suspension mechanisms is likely worn out and has excessive clearance.
The cause could be a loose strut gland nut, or something else such as a shrunken or dried out rubber bushing.
So if your car is clunking every time when it goes over bumps it's usually not a dangerous problem but you should get it checked out.
Your struts or shocks bushings are likely worn out and needs replaced and if the bushings are worn out you need to replace the entire shocks or struts.
Bad struts can also lead to problems with alignment of your vehicles wheels and could lead to uneven tire wear.
Your tie rod ends could also be worn out which need replacing as well.
I would take the car to a mechanic and have them check the suspension and tie rods out because the clunking noises is usually an easy fix.
Most times the clunking doesn't cause a dangerous situation but if your tie rods to break free then it could lead to loss of control of the vehicle.