Crossword Genius

Minute particle also called a thrombocyte crucial to the clotting of the blood of vertebrates (8)

Ross

I believe the answer is:

platelet

(Other definitions for platelet that I've seen before include "Particle of protoplasm, essential for blood clotting - tell a pet (anag)" , "Small disc in the blood" , "Disc-shaped blood cell" , "Cell fragment in the blood, important for clotting" , "something in the arteries" .)

I've seen this clue in The Mirror.
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