The most common and most likely answer to this crossword clue is the 9 letter word TRIBALISM
I've seen this crossword clue in The Times
T
R
I
B
A
L
I
S
M
More clues leading to the result TRIBALISM
- Neat, adopting island's clan system
- Border possibly limiting island's loyalty
- Island’s border crossing showing native loyalty
- Asian island is encapsulated by order and loyalty among people
- Bishop in mistrial stirred primitive allegiance?
- Clip about Asian island’s primitive behaviour
- Asian island’s in good condition making use of traditional customs
Buddy explains!

The straight part
We know that "clan system" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case clan system = tribalism.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 TRIBALISM mean?
TRIBALISM noun- The condition of being tribal.
- A feeling of identity and loyalty to one's tribe.