Books university dons borrowed from the library (3)
I believe the answer is:
out
'borrowed from the library' is the definition.
I can't judge whether this defines the answer.
'books university dons' is the wordplay.
'books' becomes 'ot' (abbreviation for Old Testament).
'university' becomes 'U' (abbreviation as in UMass).
'dons' is an insertion indicator (inserted letters wear or 'don' others).
'ot' enclosing 'u' is 'OUT'.
Can you help me to learn more?
(Other definitions for out that I've seen before include "Free" , "SECOND PART OF 14" , "SECOND PART OF 16" , "Dismissed, in cricket" , "Mistaken; unconscious" .)