Form of neuralgia (8)
I believe the answer is:
sciatica
'form of neuralgia' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sciatica that I've seen before include "I cast CIA out for this painful disorder" , "Pain from pressure on a nerve in the hip area" , "Neuralgia of the hip and thigh" , "Pain around back or hip" , "Lower back and hip pain" .)