Eager to finish early, accepting Blair perhaps brought up the central theme (7)
I believe the answer is:
keynote
'the central theme' is the definition.
(I've seen this before)
'eager to finish early accepting blair perhaps brought up' is the wordplay.
'eager' becomes 'keen' (I've seen this before).
'to finish early' means to remove the last letter (I've seen 'finishing early' mean this).
'accepting' is an insertion indicator.
'blair perhaps' becomes 'tony' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'brought up' shows that the letters should be reversed in order (down clues only).
'tony' back-to-front is 'ynot'.
'keen' with its last letter removed is 'kee'.
'kee' enclosing 'ynot' is 'KEYNOTE'.
Can you help me to learn more?
(Other definitions for keynote that I've seen before include "of fundamental importance" , "Prevailing tone or idea of a speech" , "One tyke (anag)" , "Determining principle in a speech" , "The central speech of a conference" .)