A device for processing a carcass part of slaughtered poultry, the carcass part, at the start of the process, including bone parts with at least a part of the rib cage, at least a part of the clavicle, and at least a part of the wing joint, at least a part of the outer fillet, where the part of the outer fillet that is present is connected to the part of the rib cage that is present, at least a part of the inner fillet, at least a tendon that connects the inner fillet to the wing joint, the device including an outer fillet guide to maintain at least a part of the outer fillet in the first position, a clavicle guide to hold the free ends of the wishbone in the second position, and at least one blade to cut through the tendon.