Not clear what kind of user you are talking about here, but I'm fairly certain there isn't a "clone" option for any of them.
In any case, Access Policies are defined in terms of Access Roles.
Access Roles are usually determined by querying the user in Active Directory.
For locally defined users, you can use the legacy user groups and assign those to an Access Role.
You could probably take the relevant API/CLI output of the desired user (e.g. show user name cloneme) and use that to construct the new user (e.g. set user name cloneduser ....)