Bones of the spinal column (9)
I believe the answer is:
vertebrae
'bones of the spinal column' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for vertebrae that I've seen before include "Bits of bone" , "Bits of skeleton" , "Bones of back" , "Bony segments of the spinal column" , "Backbone segments" .)