Native American doctor, one who favours war (6)
I believe the answer is:
mohawk
'native american' is the definition.
(the Mohawk are a Native American group)
'doctor one who favours war' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'one who favours war' becomes 'hawk' (someone promoting military interventions).
'mo'+'hawk'='MOHAWK'
(Other definitions for mohawk that I've seen before include "Brave" , "Iroquoian American; skating manoeuvre" , "Native American tribe" , "American runner" , "American native; skating step" .)