Starter

That single fuse powers the entire starting circuit except for the starter motor itself. To see if it is the starter solenoid or the interior wiring, replace the fuse and disconnect the brown wire from the starter solenoid and turn the key. The starter relay should click. If the fuse does not blow you have a bad starter solenoid.
If the fuse blows, pull the starter relay and test again. If it blows now you have a short from the ignition switch to the starter relay.