It is possible to install Clarity and a Ps plug-in. I am not a big fan of having to leave my usual workflow to enter Studio to use Clarity. TYIA.
Did you purchase Clarity as a plugin previously? if so, it is available at this link: https://help.topazlabs.com/hc/en-us/articles/115001521092-Previous-Versions , but it is no longer a supported product.