Relating to blood vessels (8)
I believe the answer is:
vascular
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to blood vessels</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 vascular that I've seen before include "Relating to blood vessels" , "Of vessels that circulate blood" , "Relating to vessels that circulate fluids" , "Consisting of vessels for conveying blood" , "Relating to blood-carrying vessels" .)