Possible confirmation of leader for Camelot, not united in joint complaint (9)
I believe the answer is:
arthritis
'complaint' is the definition.
(arthritis is a kind of health problem)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for arthritis that I've seen before include "Inflammation of joints" , "complaint" , "Joint pain" , "Inflammatory disease of the joints" .)