The most common and most likely answer to this crossword clue is the 9 letter word PINNACLES
P
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More clues leading to the result PINNACLES
Buddy explains!

The straight part
We know that "Peaks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case peaks = pinnacles.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 PINNACLES mean?
PINNACLES noun- The highest point.
- A tall, sharp and craggy rock or mountain.
- An all-time high; a point of greatest achievement or success.
- An upright member, generally ending in a small spire, used to finish a buttress, to constitute a part in a proportion, as where pinnacles flank a gable or spire.
- To put something on a pinnacle.
- To build or furnish with a pinnacle or pinnacles.