What's this cable and where does it has to be attached to?

[goldNSX]

Before reassembling a climate board I found a cable which I believe must be connected to mass. But I didn't take it off when removing the climate control.
What's this cable for?

 

[D'Ecosse]

I believe that's a ground wire & goes under the screw you indicated on the center bar bracket (where bottom mount of the radio & the ash-tray screws to).

 

[pelletz]

I agree

 

[dgaetano]

Yes, it's the ground. Here's a reference picture I took before removing my radio. Note that it was not attached to the screw that you have highlighted, but I'd be shocked if it made any difference.