Doctor finds rings inside entrance (4)
I believe the answer is:
door
'entrance' is the definition.
(I know that door is a type of entrance)
'doctor finds rings inside' is the wordplay.
'doctor finds' becomes 'do' (I can't explain this - if you can you should believe this answer much more).
'rings' becomes 'tori' (I've seen this in another clue).
'inside' says to take the centre.
The centre of 'tori' is 'or'.
'do'+'or'='DOOR'
Can you help me to learn more?
(Other definitions for door that I've seen before include "Threshold" , "Swinging barrier" , "Entrance way" , "Entry point" , "Portal" .)