Blood carrier (4)
I believe the answer is:
vein
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blood carrier</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for vein that I've seen before include "Deposit of mineral" , "Part of the blood circulation system" , "Seam of mineral" , "Leaf rib; ore layer in rock" , "Distinctive style" .)