Undergarment found in library! (3)
I believe the answer is:
bra
'undergarment' is the definition.
(bra is a kind of undergarment)
'in library' is the wordplay.
'in' indicates a hidden word.
'BRA' is hidden in the letters of 'library'.
'found' acts as a link.
(Other definitions for bra that I've seen before include "support" , "Female undergarment" , "one carrying chest" , "I give a couple a lift" , "Underwear item" .)