Some things you just have to accept as the way it is. Having said that, a "fusible link" is just what you described. It's a short length of smaller gauge wire spliced into the conductor. For instance a fusible link for a 10 gauge wire might have a short length of 14 or 16 gauge. Just like the fuse, there won't be an appreciable voltage drop in normal operation, but the conductor will melt if the current gets too high.