There's nothing exceptional holding in this opening feature (5)
I believe the answer is:
hinge
'this opening feature' is the definition.
(feature which lets a door open)
'there's nothing exceptional holding' is the wordplay.
'holding' indicates a hidden word.
'HINGE' is hidden within 'theres nothing exceptional'.
'in' acts as a link.
(Other definitions for hinge that I've seen before include "Circumstance upon which subsequent events depend; door facilitator" , "Joint on which something swings" , "Movable swinging joint" , "Joint on which things turn" , "door open because of this?" .)