Upper limb (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">upper limb</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for arm that I've seen before include "Supply weapons" , "Equip with a limb" , "Upper limb" , "Prime" , "Equip with weapons" .)