Smart joint? (3)
I believe the answer is:
hip
I believe this clue is a double definition.
'smart' is the first definition.
(I've seen this in another clue)
'joint?' is the second definition.
(part of body)
(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" .)