* "Wood chuk" sounds like a made-up word, so it's likely a play on words.
* "What wood" is asking for a type of wood.
Putting it together, we can guess that "wood chuk" might be a way to say "woodchuck."
The answer to the riddle is "He can chuck wood as much as a woodchuck would if a woodchuck could chuck wood."
This is a play on the classic tongue twister, "How much wood would a woodchuck chuck if a woodchuck could chuck wood?"