Fluid part of blood (6)
I believe the answer is:
plasma
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fluid part of blood</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for plasma that I've seen before include "Liquid part of blood" , "Colourless fluid in blood; green variety of quartz" , "Yellow liquid in blood" , "element of transfusion" , "Screens of some TVs" .)