Banter? None affected 12A 15 (4,6)
I believe the answer is:
Here is my best explanation:
'12a 15' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'banter? none affected' is the subsidiary indication.
'affected' indicates anagramming the letters.
'banternone' anagrammed gives 'annebronte'.
(Another definition for anne bronte that I've seen is "Agnes Grey author, d. 1849".)