Red suit
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">red suit</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 hearts that I've seen before include "quarterdeck?" , "Red playing cards" , "Card game and centres of emotions, it's said" , "not clubs" , "Scottish footballers" .)