Move close to your attacker, pre-empt them and block close to the grip or on their forearms; the club has highest speed and thus force at the tip after a full swing. Use the outer, ulna side of your arm where there’s no important blood vessels, nerves, or muscles but make contact close to the wrist where the bone’s harder to break. Mostly you’re just trying to add a vector to their swing that leaves them in an unhelpful position, but for overhead strikes you can cross your arms at the wrist and trap it in the vee