you did not post your mb model so I give it a shot. Some newer mb have post code reader. If there a fault at post it show on he LCD or led screen.
On newer mb there may be buttons to turn on the mb. Flash the mb bios or reset the mb or over clock it. The clr CMOS is called clear the CMOS.
On the mb there a chip that holds the mb settings and date and time.
Sometimes you have to clear that chip...ie over clock failure.
So you would press that button.
CLEAR CMOS = If you are unable to POST unplug the PC, press the Clear CMOS button either on the board itself or in the back where the plugs are and it will clear all customized BIOS settings hopefully allowing you to POST on restart.