Doctor brought up some rancid emetic (5)
I believe the answer is:
medic
'doctor' is the definition.
(doctor is a type of medic)
'up some rancid emetic' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'some' indicates a hidden word (some of the parts of the word are used).
'cidem' is hidden in the letters of 'rancid emetic'.
'cidem' in reverse letter order is 'MEDIC'.
'brought' acts as a link.
(Other definitions for medic that I've seen before include "Health worker" , "What was Basutoland" , "Word for 'doctor'" , "He may offer treatment" , "Physician (informal)" .)