Supporter of foul nature (4)
I believe the answer is:
ulna
'supporter' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'of foul nature' is the wordplay.
'of' says the answer is hidden in the clue.
'ULNA' can be found hidden inside 'foul nature'.
Can you help me to learn more?
(Other definitions for ulna that I've seen before include "part of arm" , "Car document; ticket book" , "Part of body" , "Radius partner" , "a section of framework" .)