Writer of nonsense needing books picked up (6)
I believe the answer is:
learnt
'picked up' is the definition.
(pick up can mean to learn or discover)
'writer of nonsense needing books' is the wordplay.
I cannot really understand how this works, but
'writer' could be 'lear' (I have seen 'comic writer' mean 'lear' so perhaps 'writer' could also mean 'lear') and 'lear' is found in the answer.
'books' could be 'nt' (abbreviation for New Testament) and 'nt' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for learnt that I've seen before include "Gained knowledge of rental" , "Committed to memory" , "Came to know" , "Gained knowledge or skill" , "Realised" .)