Hip pain (8)
I believe the answer is:
sciatica
'hip pain' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sciatica that I've seen before include "I cast CIA out for this painful disorder" , "Neuralgia of the hip and thigh" , "Type of neuritis" , "Intense pain in the leg" , "Neuralgia of the hip region" .)