The most common and most likely answer to this crossword clue is the 11 letter word HAEMOGLOBIN
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More clues leading to the result HAEMOGLOBIN
Buddy explains!
The straight part
We know that "Stuff of transfusion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stuff of transfusion = haemoglobin.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does HAEMOGLOBIN mean?
HAEMOGLOBIN noun- The iron-containing substance in red blood cells that transports oxygen from the lungs to the rest of the body; it consists of a protein (globulin), and haem (a porphyrin ring with an atom of iron at its centre).