Knocker hauled up on hill (9)
I believe the answer is:
detractor
'knocker' is the definition.
('detractor' can be a synonym of 'knocker')
'hauled up on hill' is the wordplay.
'hauled' becomes 'carted' ('cart' can be a synonym of 'haul').
'up' is a reversal indicator (in down clue: letters go upwards).
'on' is a charade indicator (letters next to each other).
'hill' becomes 'tor' (tor is a kind of hill).
'carted' reversed gives 'detrac'.
'detrac'+'tor'='DETRACTOR'
(Other definitions for detractor that I've seen before include "Critic" , "Slighter" , "I make uncomplimentary remarks" , "one responsible for mud flying around" , "One disparages or belittles" .)