Wear casual clothes (9)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wear casual clothes</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dress down that I've seen before include "Slob around" , "look less formal" , "Severely criticise" , "Put on casual clothes" , "Rebuke" .)