The most common and most likely answer to this crossword clue is the 5 letter word NAURU
I've seen this crossword clue in The Daily Telegraph
N
A
U
R
U
More clues leading to the result NAURU
- Island not displaying any aquarium oddly
- Island vessel about to be filled with gold
- Island nation never accepted ultimatum, riling union leaders
- Leading authority losing capital after backing an island nation
- Gold in vase turned up in Pacific Island
- Run around collecting gold somewhere near Hawaii
- Vessel returns, carrying gold for island country
- Small country where a spiritual teacher shaves head after meditation, finally
- North American university game and state
- Beginning to near Australia, unfortunate refugees upset to be incarcerated here
Buddy explains!

The straight part
We know that "Pacific island" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pacific island = nauru.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.