Prepared to study history at last (5)
I believe the answer is:
ready
'prepared' is the definition.
(similar in meaning)
'study history at last' is the wordplay.
'study' becomes 'read' (synonyms).
'at last' suggests the final letters.
The final letter of 'history' is 'y'.
'read'+'y'='READY'
'to' is the link.
(Other definitions for ready that I've seen before include "Suitably prepared" , "Fully prepared" , "Cash; within reach" , "Prepare < dough" , "Prompt and adequate" .)