Quiet at back of passage (5)
I believe the answer is:
shaft
'passage' is the definition.
(shaft is a kind of passage)
'quiet at back' is the wordplay.
'quiet' becomes 'sh'.
'at' is a charade indicator (letters next to each other).
'back' becomes 'aft' ('aft' is associated in meaning with 'back'**).
'sh'+'aft'='SHAFT'
'of' acts as a link.
(Other definitions for shaft that I've seen before include "Vertical passage of mine" , "Ray of light; spear" , "fleece" , "Beam - well" , "Ray (of sunlight)" .)