Bracket secures shelf (4)
I believe the answer is:
rack
'shelf' is the definition.
(thesaurus)
'bracket secures' is the wordplay.
'secures' says the answer is hidden in the clue (I've seen 'securing' mean this).
'RACK' is hidden within 'bracket'.
(Other definitions for rack that I've seen before include "Support" , "Old torture device on which victims were stretched" , "Luggage carrier - instrument of torture" , "Torture device that stretches" , "Cause of anguish" .)