Relating to the sun (5)
I believe the answer is:
solar
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to the sun</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 solar that I've seen before include "Mediaeval chamber" , "chamber in old house" , "of heavenly body" , "Pertaining to the sun" , "Of the sun, as ray or panel" .)