Fusible link?

The yellow tagged blue wire is the actual "fuse". The black plastic is the connector. You need to isolate the wire that runs from the bulkhead connector to the single black connector if you have one. It looks like yours does not have the connector shell on that wire you are pointing to. You need to open that harness up and inspect. My car had factory fusible link, and a shorted horn wire burnt all the wiring it touched in the time it took for the fusible link to open up. After much repair and wire replacement I installed a fuse holder and standard fuse instead of the factory fusible link. Many do an ammeter bypass modification to the wiring to remove this large wire from the connector and route it outside the connector through the firewall.