2002 Ford Explorer clunking noise when I first accelerate

I have noticed a "clunking" noise when I first begin to drive after I have come to a stop. It almost sounds like a stick is stuck under the vehicle and is hitting an aluminum heat guard or something. The noise disappears as I increase speed. It sounds like the noise is coming from the rear drivers side but hard to be certain. Any ideas of what this could be? Or what to check? I took off the rear passenger wheel but didn't see anything out of place, damaged or appear to be rubbing on anything. I did notice the wheel (prior to taking completely off) had some play, only an inch or so but a similar noise was heard when rotating (this could be normal?). Could it be a bad CV joint or could the rubber bushings inside the metal sleeves in the caliper? I hate to drive on it if it is unsafe, please help asap.