If it is fused and going to the front, I would guess it is for a stereo or lights.
Some light kits have a relay in them and that might be clicking when you power up. I would see if there is a negative wire trailing with it first. If so, see how many batteries they are "jumping" to attain a certain voltage. It may be a light kit that is using 2 of your batteries to get 16 volt. If you jump to another battery, you could get too much voltage and burn something up.
Trace the wires down and let us know where they go before moving anything.
Good Luck
