A vertical passageway? Quiet at the back! (5)
I believe the answer is:
shaft
'a vertical passageway?' is the definition.
'shaft' can be an answer for 'passageway?' (shaft is a kind of passageway). I'm unsure of the 'a vertical' bit.
'quiet at the back' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'at' means one lot of letters go next to another.
'the back' becomes 'aft' (at the back of a ship).
'sh'+'aft'='SHAFT'
Can you help me to learn more?
(Other definitions for shaft that I've seen before include "Ray; access hole to a mine" , "Stem, handle; (light) ray" , "Ray of light; treat unfairly" , "Ray of light; spear" , "Vertical passage of mine" .)