Old Bill's traditional name, formally (6)
I believe the answer is:
robert
'old' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'bill's traditional name formally' is the wordplay.
I cannot really understand how this works, but
'name' could be 'bert' and 'bert' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for robert that I've seen before include "- Edward Lee, US Confederate general" , "Name of three Scottish kings" , "- Browning, Eng. poet" , "-- Browning, English poet" , "See 22" .)