Relating to the moon (5)
I believe the answer is:
lunar
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to the moon</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 lunar that I've seen before include "of a circling body" , "Period of 28 days" , "Selenic" , "Moon's" , "that could describe landscape with more than one mare" .)