Try moving the wheel reflectors towards the rim to tighten the brackets up a bit. These reflectors usually just snap on the spokes, and the closer you get to the rim, the wider the spokes get from each other. It's just a "friction" fit thing. If you move the reflectors towards the rim enough to stop the clicking noise, but they eventually move back towards the center of the wheel, loosen up and make noise again, you can move them back towards the rim to silence the noise, and then just place a dab of some type of glue in front of the reflector connection to the spoke to keep it from moving towards the center again. Depending on the bicycle laws in your state, you could also just remove these reflectors if they become a bother. You can replace them with a white light in the front that also shows light 180 degrees to each side, and a red lamp in the rear that also shows red light 180 degrees. The lights are safer and more useful anyway.