The most common and most likely answer to this crossword clue is the 9 letter word POLYNESIA
I've seen this crossword clue in Financial Times
P
O
L
Y
N
E
S
I
A
More clues leading to the result POLYNESIA
- Yearn extremely to visit the ends of the earth: one reaches a group of islands
- Group of 18 down army finally captured during conflict in Spain? Olé!
- Antipodeans around here heard parrot flapping in sea
- A pony’s transformed with lei — in this Pacific region?
- One plays around island or many islands in one place?
- Reviewed noisy plea of group of islands
- I alone spy shifting group of islands
- Sly entomologist originally, with piano, composed part of South Pacific
Buddy explains!
The straight part
We know that "Group of 18 down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case group of 18 down = polynesia.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.