ALIAS is a Shell command, not a CLI command. It is not available in the initial CLI. You first have to load shell-seg as resident module and can then create a new shell using the NewShell command. Only in the new shell the ALIAS command is available.
The Shell is an improved CLI which was newly introduced in WB 1.3. It is not in Kickstart and not in 1.2. In 2.0 Shell and CLI were merged into one.
Together with the Shell a new console handler called NEWCON was introduced, too. It allows basic input editing and has a command history. It is only available if you mount it. In 2.0 NEWCON features were merged into CON and NEWCON was removed.
Furthermore you cannot define an alias for ALIAS. ALIAS is an internal command of the Shell which is handled seperately to manage entries in the alias list. An entry in the alias list however has to be a real DOS command.