Lesson doesn't start describing land for crops (6)
I believe the answer is:
arable
'land for crops' is the definition.
(I've seen this before)
'lesson doesn't start' is the wordplay.
'lesson' becomes 'parable' (I've seen this before).
'doesn't start' means to remove the first letter.
'parable' with its first letter taken away is 'ARABLE'.
'describing' is the link.
(Other definitions for arable that I've seen before include "Tillable" , "Productive" , "Like some ground" , "Cultivatable" , "Crop-land" .)