Ban, disallow (4)
I believe the answer is:
veto
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">ban</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(veto can mean a ban or prohibition on something)</span><br/ ><br/ >'<span class="explanation-format__original">disallow</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that disallow can be written as veto)</span><br/ ><br/ ></span>
(Other definitions for veto that I've seen before include "Refuse permission" , "Embargo" , "Throw out" , "Ban; refuse to allow" , "Refuse to endorse" .)