The most common and most likely answer to this crossword clue is the 11 letter word HIPPOCAMPUS
I've seen this crossword clue in The Guardian
H
I
P
P
O
C
A
M
P
U
S
Buddy explains!
The straight part
We know that "Part of the 10" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of the 10 = hippocampus.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 HIPPOCAMPUS mean?
HIPPOCAMPUS noun- A mythological creature with the front head and forelimbs of a horse and the rear of a dolphin.
- A part of the brain located inside the temporal lobe, consisting mainly of grey matter. It is a component of the limbic system and plays a role in memory and emotion.