Note superficial pollution (6)
I believe the answer is:
blight
'pollution' is the definition.
(thesaurus)
'note superficial' is the wordplay.
'note' becomes 'b' (musical note).
'superficial' becomes 'light' (light can mean superficial or trivial).
'b'+'light'='BLIGHT'
(Other definitions for blight that I've seen before include "Setback" , "Shrivelling disease" , "Affliction" , "Withering disease (in plants)" , "Pestilence - state of decay" .)