English books retained by bosses for undergraduates (8)
I believe the answer is:
students
'for undergraduates' is the definition.
(I've seen this before)
'english books retained by bosses' is the wordplay.
'english' becomes 'E' (abbreviation).
'books' becomes 'NT' (abbreviation for New Testament).
'retained by' indicates putting letters inside.
'bosses' becomes 'studs' (boss can mean a type of metal stud).
'e'+'nt'='ent'
'ent' placed inside 'studs' is 'STUDENTS'.
(Other definitions for students that I've seen before include "Teachers teach them" , "Pupils, learners" , "Learners or scholars" , "Sent dust to those who learn" , "Sent dust to the learners?" .)