Raps (6)
I believe the answer is:
knocks
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">raps</span>' is the definition.<br/ ><span class="explanation-format__explanation">('knock' can be a synonym of 'rap')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for knocks that I've seen before include "Bangs on door" , "criticisms" , "Gentle taps" , "Raps, taps" , "Reversals" .)