Disciplinarian (8)
I believe the answer is:
martinet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">disciplinarian</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for martinet that I've seen before include "Person who demands strict obedience" , "Tyrant, one who demands strict obedience" , "Gradgrind was one" , "Strict disciplinarian - met train (anag)" , "Disciplined type" .)