Specialist to see old city rings left inside substance (9)
I believe the answer is:
urologist
'specialist' is the definition.
(I know that urologist is a type of specialist)
'see old city rings left inside substance' is the wordplay.
I cannot really understand how this works, but
'see' could be 'lo' ('lo' is an archaic exclamation meaning 'look!') and 'lo' is found within the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is present in the answer.
'city' could be 'ur' (ancient Sumerian city state) and 'ur' is present in the answer.
'substance' could be 'gist' (synonyms) and 'gist' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Another definition for urologist that I've seen is " Doctor specialising in the waterworks?".)