Last spring I had a similar sound coming from my left rear..... clink, clink, clink with each tire rotation.
I get it off the ground and pulled the wheel to poke around a bit. Everything was tight and I couldn't find any slop. Frustrated, I have a look at the tire and discovered a nail head (it had had a slow leak for a while). Having given up on the source of the "clink" sound, I decide to pull the tire and patch the leak. Low and behold, the nail head turned out to be a 1/4" spike about 4" long! It was tapping the inner rim with each rotation!!
Not that this story will help much... It was a freak thing for sure! Just the same, you may want to have a look at your tire since you've probably removed the wheel.