Plug or bung (7)
I believe the answer is:
stopper
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">plug</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that stopper is a type of plug)</span><br/ ><br/ >'<span class="explanation-format__original">bung</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that Stopper is a bung)</span><br/ ><br/ ></span>
(Other definitions for stopper that I've seen before include "Perhaps cork" , "Plug for a bottle" , "One blocks" , "Maybe cork" , "Cork - goalkeeper?" .)