Silly person, old one, needing treatment (6)
I believe the answer is:
noodle
'silly person' is the definition.
The answer and definition can be both body parts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'old one needing treatment' is the wordplay.
'old one' can be anagrammed to 'NOODLE'.
But, I'm not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for noodle that I've seen before include "Ribbon-like strip of pasta" , "Simpleton - strip of pasta" , "may end up in the soup" , "String of pasta" , "Idiot" .)