I'm not sure where you'd put the hose clamps. There should be plastic (nylon) fuel lines running to the valve from both the tanks and the engine. It transitions to metal a little further down the frame rail closer to the engine.

Its quite possible one of the plastic fittings that snaps onto the valve has cracked. You can by replacements (possibly in kit form) from parts stores.

I'll third the notion to clean up the area, and find exactly where its leaking from first.