Bill blocker (3)
I believe the answer is:
nay
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bill blocker</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nay that I've seen before include "Negative answer" , "Indeed" , "telling a nicker from a pony?" , "disagreement" , "Refusal" .)