Part of blood (6)
I believe the answer is:
plasma
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">part of blood</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 plasma that I've seen before include "Clear part of blood" , "TV screen type" , "Liquid part of blood" , "Ionised gas; fluid in blood" , "Blood component and type of television" .)