Something tasty one's fed to doctor (4)
I believe the answer is:
miso
'something tasty' is the definition.
I can't judge whether this definition defines the answer.
'one's fed to doctor' is the wordplay.
'one's' becomes 'is' (Roman numeral).
'fed to' means one lot of letters goes inside another.
'doctor' becomes 'mo' (medical officer**).
'is' inserted inside 'mo' is 'MISO'.
Can you help me to learn more?
(Other definitions for miso that I've seen before include "Soya bean paste" , "Thick paste used in Japanese soups and sauces" , "Soya-beam paste" .)