A peaceful smoke (4)
I believe the answer is:
pipe
'a peaceful smoke' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for pipe that I've seen before include "Tube; wind instrument" , "chanter" , "'Tube for water or gas, say (4)'" , "Tube for conveying gas or liquid" , "Whistle" .)