Impassivity (6)
I believe the answer is:
phlegm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">impassivity</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that impassivity can be written as phlegm)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for phlegm that I've seen before include "'spit it out!'" , "Imperturbable stolidity" , "Thick mucus in throat" , "Coolness" , "Calmness of temperament" .)