War god
I think it could be either:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">war god</span>' is the definition.<br/ ><span class="explanation-format__explanation">(Mars was the Roman god of war)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for mars that I've seen before include "Roman war god; planet" , "War god - chocolate bar - spoils" , "March to the French" , "one associated with war" , "RS [RED STAR] (not technically)" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">war god</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ares that I've seen before include "Olympian" , "War-god" , "Land measures" , "figure of worship" , "Greek god of war" .)