Most of satire is smooth (4)
I believe the answer is:
iron
'is smooth' is the definition.
(thesaurus)
'most of satire' is the wordplay.
'most of' means to remove the last letter.
'satire' becomes 'irony' ('irony' can be a synonym of 'satire').
'irony' with its final letter taken away is 'IRON'.
(Other definitions for iron that I've seen before include "Metallic chemical element" , "stern" , "inflexible > club" , "Smooth - driver?" , "used in the evening" .)