The most common and most likely answer to this crossword clue is the 9 letter word AQUAPLANE
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Buddy explains!
The straight part
We know that "Water board" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case water board = aquaplane.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does AQUAPLANE mean?
AQUAPLANE noun- A board ridden by a standing person and pulled by a motorboat for entertainment
- To ride such a board
- For a car or similar vehicle to slide along the road on a thin film of water between the road and the tyres. This occurs when a car has some speed and comes to somewhere with more water on the road than the weight of the car and the grooves in the tyre tread pattern (if any) can push away. The result is almost no traction at all for steering or braking.