Prepared to study diligently, finally (5)
I believe the answer is:
ready
'prepared' is the definition.
('ready' is associated in meaning with 'prepared')
'study diligently finally' is the wordplay.
'study' becomes 'read' ('read' can be a synonym of 'study').
'finally' indicates one should take the final letters.
The last letter of 'diligently' is 'y'.
'read'+'y'='READY'
'to' acts as a link.
(Other definitions for ready that I've seen before include "In addition" , "Prepared, willing" , "Primed" , "All set to go" , "Fully prepared" .)