The most common and most likely answer to this crossword clue is the 4 letter word GUAM
I've seen this crossword clue in The Guardian
G
U
A
M
More clues leading to the result GUAM
- Island for the nobs featured in back issue of periodical
- Attack from the rear to capture a Pacific island
- Sticky substance overrunning a Pacific island
- Stick around American island
- Pacific island where American has to stick around
- Pacific island one introduced to eucalyptus
- One month and another back in US base
- Vessel carrying article to north island
- Island being ace, stick around
- Overturn vintage sports car smuggling gold in US territory
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 = guam.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.