Indicate assent (3)
I believe the answer is:
nod
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">indicate assent</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for nod that I've seen before include "OK" , "Gesture of assent" , "even Homer sometimes does" , "Gesture; agree" , "Fellow that's set up number 500" .)