Spine (8)
I believe the answer is:
backbone
'spine' is the definition.
(I know that spine can be written as backbone)
This is the entire clue.
(Other definitions for backbone that I've seen before include "Spine or courage" , "Fortitude - protection for the spinal cord" , "Lt protects the spinal cord" , "Informal courage of spinal kind" , "Strength of character" .)