It is possible that there are two earths in there. One for the clock and one for the light, a permanent live for the clock, an ignition switched live for the light and then a wire that gets connected to the side light live that dims the clock light a little bit when the lights are turned on so as not to be to bright at night. Much like the screen of your stereo.
As for what wire does what it would be pure guess work and it is very easy to fry the clock.
Is there any exposed metal part of the clock? If so you should be able to use a multimeter to check which wire is the ground by seeing which wires have continuity between the exposed metal and the ground wire.
Can you remove the lamp and see which wires that are going into the lamp holder? This might eliminate another couple of wires.
If you want me to I will make a guess at what wire does what but I would advise against it.
I'm gonna totally backtrack on what I said before Darryl. The red is the switched and the yellow is permanent live, not the other way around [:$]