Joint that’s nothing exceptional inside (5)
I believe the answer is:
hinge
'joint' is the definition.
(hinge is a kind of joint)
'that's nothing exceptional inside' is the wordplay.
'inside' says the answer is hidden in the clue.
'HINGE' is hidden within 'thats nothing exceptional'.
(Other definitions for hinge that I've seen before include "Device for letting door etc swing" , "Joint on which things turn" , "Pivotal point" , "Key principle" , "Joint on which something swings" .)