Make pleasant smell with fragrant plant (8)
I believe the answer is:
humanise
'make pleasant' is the definition.
(to make kind or humane)
'smell with fragrant plant' is the wordplay.
'smell' becomes 'hum' (I've seen this in other clues).
'with' says to put letters next to each other.
'fragrant plant' becomes 'anise'.
'hum'+'anise'='HUMANISE'
(Other definitions for humanise that I've seen before include "Make like man" , "make pleasanter?" , "Make sociable - use in ham (anag)" .)