The most common and most likely answer to this crossword clue is the 9 letter word ISTHMUSES
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Buddy explains!

The straight part
We know that "narrow strips of land" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case narrow strips of land = isthmuses.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 ISTHMUSES mean?
ISTHMUSES noun- A narrow strip of land, bordered on both sides by water, and connecting two larger landmasses.
- Any such narrow part connecting two larger structures.
- An edge in a graph whose deletion increases the number of connected components of the graph.