The same doctor briefly turned up (4)
I believe the answer is:
idem
'the same' is the definition.
(Latin for 'the same', used in citations)
'doctor briefly turned up' is the wordplay.
'doctor' becomes 'ME'.
'briefly' becomes 'di' (I am not sure about this - if you are sure you should believe this answer much more).
'turned up' 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 "The same (as that just mentioned) (Lat.)" , "The same-in Latin" , "The same as just mentioned, to old Romans" , "The same for an odd dime" , "[DOUBLE]" .)