Unwanted gas pipe? (7)
I believe the answer is:
exhaust
This clue could be a double definition.
'unwanted gas' is the first definition.
'exhaust' can be an answer for 'gas' (thesaurus). I am not certain of the 'unwanted' bit.
'pipe?' is the second definition.
(I know that exhaust is a type of pipe)
Can you help me to learn more?
(Other definitions for exhaust that I've seen before include "Car part for carrying away gases - would make you tired" , "Pipe that carries engine fumes away" , "Tire utterly or fumes-dispersing device in car" , "Wear, tire out" , "Burnt gases are discharged here" .)