Master's joint title (8)
I believe the answer is:
lordship
'title' is the definition.
(lordship is a title or form of address)
'master's joint' is the wordplay.
'master's' becomes 'lords' ('lord' can be a synonym of 'master').
'joint' becomes 'hip' (part of body).
'lords'+'hip'='LORDSHIP'
(Other definitions for lordship that I've seen before include "Dominion - authority" , "Superior state" , "Supreme rule" , "House" , "Supreme power" .)