Cruel, being puerile round unpleasant smell (8)
I believe the answer is:
inhumane
'cruel' is the definition.
(similar in meaning)
'puerile round unpleasant smell' is the wordplay.
'puerile' becomes 'inane' (I've seen this in another clue).
'round' is an insertion indicator.
'unpleasant smell' becomes 'hum' (hum can mean a disgusting smell).
'inane' enclosing 'hum' is 'INHUMANE'.
'being' acts as a link.
(Other definitions for inhumane that I've seen before include "Heartless" , "Callous" , "Cruel" , "Not compassionate" .)