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: Topaz Labs , but it is no longer a supported product.
You can go directly to Clarity from PS via the Filters menu:
If you prefer the old plug-in method but don’t own it I believe you can get a licence for it if you own the adjustment (but as Larry says it’s no longer supported).