The problem you are having with the clock and the dash lights is most likely to a defective headlight switch. There is a 20 amp circuit breaker inside the headlight switch that powers the clock and the stop light circuit. Make sure both of these circuits are not causing the circuit breaker inside the headlight switch to cycle on and off before replacing the headlight switch.
The dash lights are powered through a rheostat on the front of the headlight switch. If the dash lights do not work, make sure you rotate the headlight switch while checking. If they do not work or work intermittently, check for continuity between terminal R (black wire) and terminal I (blue wire with red band) of the headlight switch while rotating the rheostat. If no continuity, replace switch.
The fuse on the headlight switch that icarch mentioned in his post only powers the courtesy lamp in the dash and the door jamb switches. If this is blown, check the wiring to the map light and door switches for bare wires especially where the wires exit the kick panels and enter the door jamb.
Hope this information helps.
doug7740
1955 Thunderbird Blue