Surface for a surfer (4)
(Other definitions for wave that I've seen before include "Greeting hand gesture" , "Undulating curve" , "Billow" , "Drive forward" , "60s cinematic movement with 1a [NEW]" .)
(Other definitions for board that I've seen before include "Plank" , "panel" , "Supervisory committee" , "See 21 Down" , "See 9" .)