Hello. I think this is the normal and expected behavior. bin/console cache:clear is a console command, so it must boot the kernel in order to work. And to boot the kernel, it will use the cached container, which require all env vars. If you rename a variable in the .env, the container in the cache will still need the previous variable.

In dev environnement it works because the container is rebuilt a each request / command exec, so it doesn't try to boot the cached container with the old env var.

I think the proper way to rename an env var is to push the new variable in production, keeping the old one, and then remove it in a second time.

Maxime is right.
We might also wonder why accessing the env var is needed at this stage. Not sure it's legit.

The same kind of error occurs when updating packages that no longer have the code corresponding to the cache.
Perhaps we need a special system for the cache:clear command.