You want to know if you can manually download and update the definition for "Web and Cloud Security Protection".
Release: 14.3 RU2 and later.
Web and Cloud Access Protection was renamed from Network Traffic Redirection in 14.3 RU2.
You have an unmanaged SEP client and no internet connection.
You are manually updating Virus definition and Security updates using this KB article but, you can not see any option to manually update "Web and Cloud Access Protection".
Web and Cloud Access Protection definitions are not available for manual download, or via Intelligent Updater.
The content/definition can only be downloaded and updated by LiveUpdate or Internal Liveupdate Administrator.