Is there a Usenet newsgroup on CA-Clipper?

 Yes.

 comp.lang.clipper is the major one.  If you count alt groups,
 there's also alt.comp.databases.xbase.clipper, but that
 group is being abandoned by most users.

 I am also working on an RFD for comp.softsys.app-builder.visual-objects
 for VO discussions.