Smell a new being (5)
I believe the answer is:
human
'being' is the definition.
(human is a kind of being)
'smell a new' is the wordplay.
'smell' becomes 'hum' (I have seen 'Unpleasant smell ' mean 'hum' so perhaps 'smell' could also mean 'hum').
'a new' becomes 'an' (I've seen this in other clues).
'hum'+'an'='HUMAN'
(Other definitions for human that I've seen before include "Being that's apt to err?" , "Like people" , "Relating to people" , "Man, woman or child" , "Genial, kind" .)