Warmth of passion (6)
I believe the answer is:
ardour
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">warmth of passion</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 ardour that I've seen before include "Intense eagerness" , "Enthusiasm or warmth of passion" , "causing some heat" , "Passionate zeal" , "Warm, passionate feeling" .)