Yes, you can have the AP use VLAN x as the native VLAN on a trunk and thats where it will get it's IP address. You can then create a bridge mode SSID and place VLAN y in the VAP configuration. Users that connect to the bridge mode SSID will have their traffic tagged (802.1q) with VLAN y and sent to your access switch.
The port on the access switch must be in trunk mode and have VLAN x as the native and allow VLAN y on the trunk.