Atlantic, say (5)
I believe the answer is:
ocean
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">atlantic say</span>' is the definition.<br/ ><span class="explanation-format__explanation">(atlantic is a kind of ocean)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ocean that I've seen before include "Quantity of water" , "Large area of water" , "Large expanse of sea" , "Huge sea" , "Salt water expanse" .)