The most common and most likely answer to this crossword clue is the 9 letter word GALLERIES
I've seen this crossword clue in The Daily Telegraph
G
A
L
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E
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Buddy explains!
The straight part
We know that "long passages" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case long passages = galleries.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 GALLERIES mean?
GALLERIES noun- An institution, building, or room for the exhibition and conservation of works of art.
- An establishment that buys, sells, and displays works of art.
- The uppermost seating area projecting from the rear or side walls of a theater, concert hall, or auditorium.
- The, often elevated and in the rear, part of a courtroom where seating for the public audience is facilitated during trial.
- A roofed promenade, especially one extending along the wall of a building and supported by arches or columns on the outer side
- The spectators of an event, collectively.
- A browsable collection of images, font styles, etc.
- (fortification) A covered passage cut through the earth or masonry.
- A level or drive in a mine.