Assuming that list came from running pyenv virtualenvs, you should be able to run
pyenv uninstall 3.8.2/envs/greenhouse
to remove the 3.8.2/envs/greenhouse environment.
The environments themselves should be subdirectories of whatever pyenv root returns when you run it. Try doing cd $(pyenv root) and then looking in the versions/ and versions/{version}/envs/ subdirectories.
See the documentation for more details.