The most common and most likely answer to this crossword clue is the 6 letter word SPINES
S
P
I
N
E
S
More clues leading to the result SPINES
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The straight part
We know that "mountain ridges" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mountain ridges = spines.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 SPINES mean?
SPINES noun- The series of bones situated at the back from the head to the pelvis of a person, or from the head to the tail of an animal; backbone, vertebral column.
- Something resembling a backbone, such as a ridge, or a long, central structure from which other structures radiate.
- A pointed, fairly rigid protuberance or needle-like structure on an animal, shell, or plant.
- The heartwood of trees.
- Courage or assertiveness.
- The stiffness of an arrow.