Chimney output (5)
I believe the answer is:
smoke
'chimney output' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for smoke that I've seen before include "'There's no . . . . . without fire'" , "Cure (eg, herring)" , "Product of combustion" , "Use cigarettes" , "cause of a cough?" .)