Take on a joint (8)
I believe the answer is:
shoulder
This clue is a double definition.
'take on' is the first definition.
(I've seen this before)
'a joint' is the second definition.
(I know that shoulder is a type of ball and socket joint)
(Other definitions for shoulder that I've seen before include "Joint - ours held (anag)" , "Cut of meat" , "See 10" , "cut of beef" , "Upper body joint" .)