That's a clip to loosely retain the fuel drain line. There should be a rubber hose coming down from under the left plastic fairing above it. It is something you want.
Pull off the left plastic fairing and post a picture of what you've got. There are 2 hex head screws on the top surface of the fairing and a couple of those plastic reusable pop rivets forward and hiding on a down facing surface. Also a couple of rubber friction doodads which require careful pulling. Once you have that off you can see if you have the charcoal canister which is the California model, or a little white plastic tank that would hold maybe an ounce. Out of the bottom of whichever you have there should be a fuel drain line running down through that clip you have.
If the fuel tank overflows with the cap closed, this is where the fuel comes out. If your tank is quite full and then sits in the sun, the fuel expands and escapes via a small pressure relief valve in the fuel cap mounting. Without any drain line at all the fuel would spill onto the engine! Hopefully you have the line from the tank to whatever plumbing is under your left fairing. Without the drain line down to the ground, excess fuel can spill down the left side of the engine area.