Of the sun (5)
I believe the answer is:
solar
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">of the sun</span>' is the definition.<br/ ><span class="explanation-format__explanation">(solar means relating to the sun)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for solar that I've seen before include "Sort of power" , "sunny?" , "Powered by the sun" , "Of the sun, as ray or panel" , "Coming from the sun" .)