Somewhere in the circuit must be shorted to earth between the fuse and the lights. Is the fuse only for the dash lights or does it protect any other circuit?

Best bet would be to disconnect all items on the circuit and replace the fuse. If it blows then it’s a wiring problem, if not start plugging the components on the circuit back in, if the fuse blows then you will know where the short is. Would also make the job easier if you had a wiring diagram.

You could also try connecting a bulb across the fuse contacts to save you keep blowing fuses. The bulb should light up as the circuit is shorted to earth. Remove components on the circuit one by one and see if the bulb goes out/goes dimmer. Also try moving the loom around at various points whilst watching the bulb, if it goes out/flickers then you are in the area of the short.