I am doing a horror thing, I want a severed head that can be control in cc4. is that possible to have a normal head but without the body?

I wonder if simply deleting the body in GOZ zbrush and building missing parts of the neck would work.

Go into the materials tab and select all materials of the body arms, legs, and nails. Go to Material settings and slide the opacity slider to 0. This leaves you with a head model including the neck and a portion of the shoulders.
Select "Edit Mesh" in the modify tab and select "Sculpt" tab and click on the eyeball. This is the Show/Hide tool. 
Use your mouse to select which faces you want to hide. 
This will give you the result you need. 

I have this experimental cloth patch for the neck made with Blender pipeline by replicating part of the head, separating as a cloth and adding a mesh for severed area.
https://drive.google.com/file/d/103ImWC-oj6fJBX0vgsdskjJw19dG2o8H/view?usp=drive_link

I do not have a zbrush but you might create something similar with GOZ (not sure if DHS for cloth could be translated back to CC with GOZ).

The patch is similar to the those I have in this pack, but I never included neck patch to that pack.
Patch can be applied to any character but you have to match the adjoining texture and DHS parameters.
For properly applying texture to the neck patch check this video: https://youtu.be/8NbX-lOk0OY
This item is delicate and needs to be handled with care. Some other rules in the description at the pack link above.
May not look well if subdivided.

Texture for severed part is from different project. Slight tweaking might require or you can make your own.

So in the end it might look like that (warning: graphic imagery content):