What specifically are you wanting to delete? Note that the registry has a lifetime of the page unless the data is part of the registry cache.
I.e. I can set Registry::set('foo', 'bar') and I can Registry::get('foo') in that current page load, but on subsequent page loads it is not set.
If you are trying to set something for your products you can either add the field to one of the internal caches or you can initialize it in your init.php file or from a function within your addon.