Prepare for war (3)
I believe the answer is:
arm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">prepare for war</span>' is the definition.<br/ ><span class="explanation-format__explanation">(as in arming with weapons)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for arm that I've seen before include "Limb; weapon" , "Division of company" , "Limb or branch" , "Maybe rifle" , "Authority" .)