Pipe for smoke removal disappeared, we hear (4)
I believe the answer is:
flue
'pipe for smoke removal' is the definition.
(flue can mean a smoke duct)
'disappeared we hear' is the wordplay.
'disappeared' becomes 'flew' (fly can mean to disappear or run away).
'we hear' indicates a 'sounds like' (homophone) clue.
'flew' is a homophone of 'FLUE'.
(Other definitions for flue that I've seen before include "Air vent" , "Chimney-duct" , "Escape" , "Chimney passage" , "Chimney duct" .)