Area around the mouth (5)
I believe the answer is:
delta
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">area around the mouth</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 delta that I've seen before include "Code word for D" , "Area of alluvial deposit" , "Fourth Greek letter? - area at river mouth" , "The Greek D (5)" , "first used by Daedalus" .)