Doctor is in some dictionaries (5)
I believe the answer is:
medic
'doctor' is the definition.
(doctor is a type of medic)
'in some dictionaries' is the wordplay.
'in' says the answer is hidden in the clue.
'MEDIC' is hidden within 'some dictionaries'.
'is' acts as a link.
(Other definitions for medic that I've seen before include "Word for 'doctor'" , "What was Basutoland" , "He may offer treatment" , "Health worker" , "Eg, doctor" .)