One learning from on-line books by boss (7)
I believe the answer is:
student
'one learning' is the definition.
'on-line books by boss' is the wordplay.
'on-line' becomes 'e' (abbreviation for electronic, e.g. in ecommerce).
'books' becomes 'nt' (New Testament).
'by' is a charade indicator (letters next to each other).
'boss' becomes 'stud' ('stud' can be a synonym of 'boss'**).
'e'+'nt'='ent'
'ent' after 'stud' is 'STUDENT'.
'from' is the link.
(Other definitions for student that I've seen before include "A learner as at school" , "Eg, undergraduate" , "One in higher education" , "collegian" , "Learner, pupil" .)