G, in C (3)
I believe the answer is:
sol
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">g in c</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 sol that I've seen before include "Note - colloid - the Sun" , "Roman counterpart of Helios" , "Musical note" , "The sun in 12 Across" , "Personification of the sun" .)