Joint auditor’s born in France (4)
I believe the answer is:
knee
'joint' is the definition.
(knee is a kind of joint)
'auditor's born in france' is the wordplay.
'auditor's' becomes 'k' (I am not sure about this - if you are sure you should believe this answer much more).
'born in france' becomes 'nee' ('born' in French - 'originally named' in English).
'k'+'nee'='KNEE'
Can you help me to learn more?
(Other definitions for knee that I've seen before include "One has a cap" , "This is capped by the patella" , "Leg?joint" , "Major joint in leg" , "One bent in genuflection" .)