What does the white wire clip to?

I'm still at a loss as to where this wire goes? Now I noticed another problem. I just connected the connections on the back of the dash cluster before I secure it and put power to battery to see if my gauges work. Well all my gauges work but when I turn on the headlights and adjust dimmer switch to full don't have any dash cluster lights? When I turn my headlight switch all the way to the left my dome light comes on as it should. Is something not hooked up? I had them before? Could this have something to do with the white wire not being connected? I'm totally stumped.

Carl