Compulsory military service (12)
I believe the answer is:
conscription
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">compulsory military service</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for conscription that I've seen before include "Compulsory enlistment" , "Draft" .)