If you want Metasploit Pro to communicate over TCP without encryption, you can set it to use HTTP payloads. HTTP payloads are useful for client-side attacks or social engineering campaigns. They are the most reliable way to communicate with a target machine, but they do not provide any level of stealth.
For example, if a victim is behind a proxy and has to use the proxy to connect back to the attacking machine, you should enable the HTTP payload option. This ensures that Metasploit can create a connection between attacker and the victim.