Wave with white crest (7)
I believe the answer is:
breaker
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wave with white crest</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for breaker that I've seen before include "White-topped wave" , "User of CB radio" , "Heavy wave arriving on the shore" , "Wave with white crest" , "Roller?" .)