The most common and most likely answer to this crossword clue is the 9 letter word RETICULUM
I've seen this crossword clue in The Daily Telegraph
R
E
T
I
C
U
L
U
M
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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 RETICULUM mean?
RETICULUM noun- A network.
- A pattern of interconnected objects.
- The second compartment of the stomach of a cow or other ruminant.