Closing section of shelf in a library (5)
I believe the answer is:
final
'closing' is the definition.
('final' can be similar in meaning to 'closing')
'section of shelf in a library' is the wordplay.
'section of' indicates a hidden word.
'FINAL' can be found hidden inside 'shelf in a library'.
(Other definitions for final that I've seen before include "Last in a series of games or contests" , "The last exam or leg of competition" , "Last match in a competition" , "Concluding" , "binding" .)