Phlegm (5)
I believe the answer is:
mucus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">phlegm</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 mucus that I've seen before include "Slimy secreted bodily fluid" , "Phlegm" , "Slimy fluid secreted in the body" , "Snot" , "Slimy secretion of nose" .)