To a militarist, an awful approach to government (15)
I believe the answer is:
totalitarianism
'approach to government' is the definition.
(totalitarianism is a system of government)
'to a militarist an awful' is the wordplay.
'awful' is an anagram indicator.
'a'+'militarist'+'an'='amilitaristan'
'amilitaristan' anagrammed gives 'talitarianism'.
'to'+'talitarianism'='TOTALITARIANISM'
(Other definitions for totalitarianism that I've seen before include "Allowing no opposition" , "Dictatorship" .)