[Sidecar Bob]

It is actually retained by an M6x22mm flange head screw (it needs a 10mm wrench but the size of a screw/bolt is always the diameter of the shank, not the head size).
I can't say for sure about your CX but on the GL500 & CX/GL650 models the cable is retained by an M5x20 JIS pan head screw that goes in from the opposite side and it is possible to to reach behind the radiator with a long screwdriver to undo it. I did that once and getting the screw out was easy but I spent more time trying to get thew new cable in place than it would have taken to remove the radiator (which I ended up doing anyway).

BTW: This would be a good time to add your location and your bike's model and model year (not year first registered as UK paperwork shows) to your profile as I asked you to do when you joined 2 and a half years ago (see Forum Settings link in my signature).

 

[Sidecar Bob]

By definition a bolt is something that screws into a nut and a screw is something that screws into anything except a nut (think of them like Schroedinger's fasteners - they could be either screws or bolts until you screw them into something).
Since this particular one screws into the camshaft holder it is a screw.

And it is NOT a 10mm. As I said, the size is determined by the diameter of the shank, not the head (wrench) size. In fact, these bikes have some M6 (=6mm) screws/bolts with 10mm heads and some with 8mm heads.
Thinking of bolts by the head (wrench) size is lazy and dangerous. Many people have used the torque specified for 10mm bolts on 6mm ones and then come crying on the forum because they broke.

A "signature" is the block of text &/or images that (if set up) appears at the bottom every time you post something. In my case there is a 99% image on the right and descriptions of my bikes plus several links on the left. The link at the bottom (in bright pink) is the one you want.