I would remove the fuse and connect a bulb across the fuse contacts. If the circuit is shorted to earth the bulb will light up. Go around the lights/loads that are connected to the circuit and disconnect them. When you find the short and disconnect it the bulb will go out or glow very faintly as there is still some current passing through the other loads on the circuit.

If you disconnect all the loads on the circuit and the bulb is still on then there is a short to earth in the wiring between the fuse and the loads on the circuit. Go around various parts of the loom and move it about. When the bulb flickers or goes out you will be around the area of the short.

The diagram below shows that if there is either a short to earth, a short across a bulb holder (water ingress into bulb holder) or a faulty bulb the test bulb will light up. Remove the short and it will go out or go alot dimmer.