'depressed' and 'pressed' mean the same thing.
Yes, the RPM is not supposed to go down, it should stay between 800-850 RPM. What I was trying to say is that if RPM drops too low and the car begins to stall then the system is designed to disengage the compressor momentarily to stabilize RPM.
But since you say RPM is stable, that is not the case here.
The sound going away when clutch pedal is depressed is strange. But I am pretty sure that the 'kar kar sound is a bearing. Since it happens when the AC is turned on, I would start by checking compressor clutch and idler pulley first and then move on to other things.
Posting a video would help in diagnosing the problem.