Use domain for one site within single tenant

I've never had to deal with domains, etc - until I was asked this by our business users.....

I recently re-created a former WordPress site as a SPO site.  The business users are requesting to redirect the previous domain URL to point to the new SPO site.  We use a single tenant for our SPO environment.  

Is it possible to have a domain point to a single internal site, including the SSL cert, without impacting the rest of the tenant?

If so - what do I need to do?  Thank you in advance!