The same doctor cut back (4)
I believe the answer is:
idem
'the same' is the definition.
(Latin for 'the same', used in citations)
'doctor cut back' is the wordplay.
'doctor' becomes 'ME'.
'cut' becomes 'di' (I am not sure about this - if you are sure you should believe this answer much more).
'back' says the letters should be written in reverse.
'me'+'di'='medi'
'medi' in reverse letter order is 'IDEM'.
Can you help me to learn more?
(Other definitions for idem that I've seen before include "No longer employed" , "The same (as that just mentioned) (Lat.)" , "The same for an odd dime" , "Ditto for a dime" , "The same-in Latin" .)