Yes you can. But that client will have no filtering from Pi-Hole. I may have misunderstood what you want to do.
If you use Pi-Hole as your DHCP server, you can use dnsmasq settings to specify an alternate DNS for clients by MAC address - these clients will not use Pi-Hole.
You can also manually assign DNS on the client, and that will also result in that client bypassing Pi-Hole.