Accustom (5)
I believe the answer is:
inure
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">accustom</span>' is the definition.<br/ ><span class="explanation-format__explanation">(inuring is a kind of accustoming)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for inure that I've seen before include "Harden or season" , "Cause to become hardened to" , "Temper, toughen" , "Steel" , "Come to accept" .)