Joint of pork can provide sustenance at last (4)
I believe the answer is:
knee
'joint' is the definition.
(I know that knee is a type of joint)
'pork can provide sustenance at last' is the wordplay.
'at last' says to take the final letters.
The final letters of 'pork can provide sustenance' are 'KNEE'.
'of' is the link.
(Other definitions for knee that I've seen before include "Where the femur meets the tibia" , "joint input" , "may present problem to maid" , "Hinge joint" , "Capped joint?" .)