Surf sound (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">surf sound</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 roar that I've seen before include "Lion's cry" , "Yell" , "Bawl, bellow" , "Make a loud noise" , "Make loud angry sound like lion" .)