Cultivated land until Thursday, only partly (5)
I believe the answer is:
tilth
'cultivated land' is the definition.
('tilth' can be a synonym of 'cultivated land')
'until thursday only partly' is the wordplay.
'only partly' indicates the answer is hidden within the clue.
'TILTH' is hidden in the letters of 'until thursday'.
(Other definitions for tilth that I've seen before include "Sort of soil" , "sow here" , "Cultivated land" , "Arable land that is worked by ploughing and sowing" , "Cultivate" .)