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

I am preparing a file for printing that uses CMYK printing with a metallic ink pantone image over the CMYK. The printing agency requires the CMYK background only underneath the pantone design to be removed while keeping visible the rest of the CMYK layers that are not covered by the pantone image. Is there a simple way of doing this?

For example, imagine the file is a blue square. The blue square is CMYK and I have a red pantone circle as its own channel over the blue square. How can I remove the exact area of blue in the CMYK layer behind the pantone circle? In my actual file the "red circle" is a much more complex image. 

I look forward to hearing your thoughts. Thank you!