The most common and most likely answer to this crossword clue is the 7 plus 5 letter word WESTERN SAMOA
W
E
S
T
E
R
N
S
A
M
O
A
More clues leading to the result WESTERN SAMOA
Buddy explains!
The straight part
We know that "country once" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case country once = western samoa.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.