Time to put it up on a set of ramps and look at the exhaust for loose shields. Something that 'clunks' is usually u-joints or diff, but since the OP didn't post mileage, AT/MT or other information, I'm going to guess exhaust shields.
OP, as a suggestion, when asking for help, try posting more information other than what you posted. Details like milage, transmission type, any mods would help us give you a logical answer and will leave you less open to troll responses.
