Land cultivation hard on slope (5)
I believe the answer is:
tilth
'land cultivation' is the definition.
(another term for tillage)
'hard on slope' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'on' says to put letters next to each other.
'slope' becomes 'tilt' (I've seen this before).
'h' after 'tilt' is 'TILTH'.
(Other definitions for tilth that I've seen before include "Cultivate" , "Arable land that is worked by ploughing and sowing" , "Cultivated land" , "Ploughed land" , "Sort of soil" .)