Prepared to study a key part (5)
I believe the answer is:
ready
'prepared' is the definition.
(similar in meaning)
'study a key part' is the wordplay.
'study' becomes 'read' (synonyms).
'a key part' becomes 'y' (I can't explain this - if you can you should give a lot more credence to this answer).
'read'+'y'='READY'
'to' is the link.
Can you help me to learn more?
(Other definitions for ready that I've seen before include "At hand" , "Willing (to do something), prepare" , "Prepare < dough" , "bread" , "Suitably prepared" .)