How to eliminate CMYK colors behind pantone channel design without erasing whole CMYK layer?

I think you'll need to add a mask layer beneath the pantone layer and above the CMYK 

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer:: co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

Here is an short explanation of trapping (with regard to CMYK, but the principles can pretty much be applied to Spot Colors). 

https://helpx.adobe.com/photoshop/using/printing-images-commercial-printing-press.html#prepare_an_image_with_spot_channels_for_printing_from_another_application

Edit: 

Was there a reason to post this inquiry four times?

Could you please post screenshots with the pertinent Panels (Toolbar, Layers, Channels, Options Bar, …) visible? 

Load the Spot Channel as a Selection, invert the Selection and create a white Solid Color Layer. 

With Spott Channel areas of other values than 100% this naturally can become pretty nonsensical.

Anti-aliased edges should not be an issue themselves but you may want to employ trapping for the spot color – most likely choking the knock-out for a metallic color:

Best ask the print provider about how much to contract the knock-out.