Odour, scent (5)
I believe the answer is:
smell
I believe this clue is a double definition.
'odour' is the first definition.
(I know that odour can be written as smell)
'scent' is the second definition.
(I know that scent is a kind of smell)
(Other definitions for smell that I've seen before include "Nasal sense" , "Sniff" , "Scent" , "Hum" , "Unpleasant odour" .)