The most common and most likely answer to this crossword clue is the 7 letter word SALAMIS
I've seen this crossword clue in The Daily Telegraph
S
A
L
A
M
I
S
Buddy explains!

The straight part
We know that "island" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case island = salamis.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 SALAMIS mean?
SALAMIS noun- A large cured meat sausage of Italian origin, served in slices.
- A grand slam.
- A penis.