The most common and most likely answer to this crossword clue is the 7 letter word AREAWAY
I've seen this crossword clue in Independent
A
R
E
A
W
A
Y
Buddy explains!

The straight part
We know that "Passage" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case passage = areaway.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 AREAWAY mean?
AREAWAY noun- An outdoor passage offering access to a basement.