I already host a few domains on my ClearOS box with no problems, but they are all hosted on the Clear box itself. I recently had the need to point a subdomain to another machine on my network. In Apache2 this is reverse proxy (pointing a domain/subdomain to an internal IP address). A few Googles here and there and all I could find was a few 3-4 year old posts regarding the topic. It mentions installing and building Pound, and a few other options. None of those seemed to be right. A bit more Googling and I finally found it. Its super easy.
All I had to do was modify my existing /etc/httpd/conf.d/flex-80.conf file, nothing to install.
ProxyPass / http://localIP/
ProxyPassReverse / http://localIP/
CustomLog "logs/app.localhost-access_log_log" common
Heres where I found the solution
The forum support for ClearOS sucks, and everything I find is years old. Hopefully this helps someone, this solution worked for me using ClearOS 6.5 (as of 12/2014).