Sexual impulse (6)
I believe the answer is:
libido
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sexual impulse</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for libido that I've seen before include "Strong urge" , "Sexual impulse" , "Sexual drive" , "Emotional energy associated with sexual desire" , "Sexual or psychological urge" .)