Shock or overwhelm (4)
I believe the answer is:
stun
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">shock</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(both can mean to surprise)</span><br/ ><br/ >'<span class="explanation-format__original">overwhelm</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for stun that I've seen before include "Stupefy - daze" , "Render temporarily senseless" , "deliver a knock-out blow" , "Render insensitive" , "Bowl over" .)