The most common and most likely answer to this crossword clue is the 10 letter word ORGANELLES
I've seen this crossword clue in The Guardian
O
R
G
A
N
E
L
L
E
S
Buddy explains!

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 ORGANELLES mean?
ORGANELLES noun- A specialized structure found inside cells that carries out a specific life process (e.g. ribosomes, vacuoles).