Which muscle acts as a synergist to the flexor carpi radialis during abduction of the wrist?

The muscle that acts as a synergist to the flexor carpi radialis during wrist abduction is the extensor carpi radialis longus. Both muscles work together to assist in the movement, with the flexor carpi radialis contributing to wrist flexion and abduction, while the extensor carpi radialis longus helps stabilize and support the wrist during this motion.