Really, really big (7)
I believe the answer is:
oceanic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">really really big</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 oceanic that I've seen before include "Relating to large areas of sea" , "Pertaining to the sea" , "Relating to, eg, Atlantic or Pacific" , "overwhelming" , "Relating to great seas" .)