The clunk noise probably isn't the issue, just if the starter is slow you can hear them. If when you turn the key there's just a tick or clunk from the engine bay it's usually the starter solenoid making it. Sometimes they go bad.

The first thing you should do is remove the earth straps from the engine and starter and clean up the faces to shiny metal.
If you have some long jumper cables you can put power directly to the starter. I would also run the black jumper from the battery to the engine block near the starter.If it jumps to life it's ok and the issue is probably the power or earth leads