Trainee boss needs introduction to economics books (7)
I believe the answer is:
student
'trainee' is the definition.
(I've seen this before)
'boss needs introduction to economics books' is the wordplay.
'boss' becomes 'stud' ('stud' can be a synonym of 'boss'**).
'needs' means one lot of letters go next to another.
'introduction to' says to take the initial letters (I've seen 'introductions to' mean this).
'books' becomes 'nt' (New Testament).
The first letter of 'economics' is 'e'.
'stud'+'e'+'nt'='STUDENT'
(Other definitions for student that I've seen before include "collegian" , "Trainee" , "Scholar" , "Person engaged in learning" , "Undergraduate maybe" .)