Writer not into books originally (3)
I believe the answer is:
Here is my best explanation:
'writer' is the definition.
'not into books originally' is the subsidiary indication.
'originally' indicates taking the first letters.
The initial letters of 'not into books' is 'nib'.
(Other definitions for nib that I've seen before include "Pen-tip", "Writing tip of old pen", "Pen point", "Point of an old-fashioned pen", "Tip of pen", "Part of a fountain pen", "Pen's point", "Pen end", "Pen tip" and "Writing point of old pen".)