Cresting wave (7)
I believe the answer is:
breaker
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cresting wave</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for breaker that I've seen before include "Roller?" , "one stopping, might you say?" , "User of CB radio" , "Wave with white crest" , "A large wave, sounds destructive" .)