Smart joint? (3)
I believe the answer is:
hip
I believe this is a double definition.
'smart' is the first definition.
(thesaurus)
'joint?' is the second definition.
(hip is a kind of joint)
(Other definitions for hip that I've seen before include "Swinging" , "Fruit of a rose plant" , "Side of body - very sophisticated" , "Fashionable" , "Body part; cool" .)