Failed to be ready for new phase of agriculture? (8)
I believe the answer is:
ploughed
This clue is a double definition.
'failed' is the first definition.
(plough can informally mean to fail an exam)
'ready for new phase of agriculture?' is the second definition.
'to be' acts as a link.
(Other definitions for ploughed that I've seen before include "Turned over earth with bladed implement" , "Broke earth and turned it over" , "Churned up (of soil)" , "Worked in a particular field" , "Turned over soil with bladed farm implement" .)