Slope on hard cultivated land (5)
I believe the answer is:
tilth
'cultivated land' is the definition.
('tilth' can be a synonym of 'cultivated land')
'slope on hard' is the wordplay.
'slope' becomes 'tilt' (I've seen this before).
'on' says to put letters next to each other.
'hard' becomes 'h'.
'tilt'+'h'='TILTH'
(Other definitions for tilth that I've seen before include "Ploughed land" , "Cultivate" , "Sort of soil" , "Arable land that is worked by ploughing and sowing" , "sow here" .)