The most common and most likely answer to this crossword clue is the 8 letter word HEDGEROW
I've seen this crossword clue in Financial Times
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More clues leading to the result HEDGEROW
- Evade argument for shrubby border
- Line of plants in border region initially brought into question
- Way in which slow mover enters boundary?
- Where God arranged protection for wildlife
- How to shelter border road initially? This’ll do it
- Natural boundary providing advantage in hotel dispute
- Question about rampant greed that divides the land?
- Sit on the fence with dispute between neighbours, perhaps
- How to maintain advantage associated with river habitat for wildlife?
- Boundary stall leads to argument
Buddy explains!

The straight part
We know that "Natural boundary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case natural boundary = hedgerow.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 HEDGEROW mean?
HEDGEROW noun- A row of closely planted bushes or trees forming a hedge