Last two-thirds of manual redefined section of framework (4)
I believe the answer is:
ulna
'last' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ulna that I've seen before include "Inner bone of the human forearm" , "The longer and inner bone in forearm" , "One of two bones of the forearm" , "Thinner of two long bones in forearm" , "Radius partner" .)