Study not productive involving reading primarily (5)
I believe the answer is:
learn
'study' is the definition.
(I know that study is a more specific form of learn)
'not productive involving reading primarily' is the wordplay.
'not productive' becomes 'lean' (I can't explain this - if you can you should give a lot more credence to this answer).
'involving' indicates putting letters inside.
'primarily' says to take the initial letters.
The initial letter of 'reading' is 'r'.
'lean' going around 'r' is 'LEARN'.
Can you help me to learn more?
(Other definitions for learn that I've seen before include "Commit to memory" , "Acquire 28 across" , "what pupils do in schools" , "be taught a lesson" , "Discover - study" .)