Bone sets, closes around hip at the centre (7)
I believe the answer is:
ossicle
'bone' is the definition.
(ossicle is a kind of bone)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ossicle that I've seen before include "Small bone, especially one in the middle ear" , "Very small bone, in the middle ear say" , "A hammer" .)