This is a Teac Amplifier model AG-V8525 - the question is in the Memory Compact Flash category - but no matter - I have solved your riddle - and 2 minutes of searching (why you could not have done this yourself is a mystery to me) provides this answer...
"Protection" is an indicator that there are either shorted speaker outputs inside the unit, a shorted speaker wire, or a blown speaker connected to the unit.
Unplug the unit from AC power for 30 minutes, and disconnect all of the speakers and other associated equipment.
Upon plugging back in, press and hold the power button at the same time for 5-10 seconds to force a hard reset.
If the unit starts up normally start connecting the speakers one at a time (shutting the power down before connecting each one), until one of the speakers causes the "Protection" indicator to come on. This speaker is faulty and would need to be replaced.
If the unit shows "Protection" with NO speakers connected, then it needs the output transistors replaced inside the unit.
These directly drive the loudspeaker outputs on the receiver itself, and one or more of them being shorted (closed circuit), will trigger the error on the display of the receiver, and it will not go off until the problem is repaired. They are not user-replaceable as they are PCB mounted, and thermally coupled to a heatsink. In this case, the unit is in need of service.
The question about a Fuse requires no answer - if there were a fuse and it had blown you would not see the display you report.