I appreciate that! (6)
I believe the answer is:
thanks
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">i appreciate that</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 thanks that I've seen before include "Polite acknowledgment" , "recognition?" , "Word of appreciation" , "Ta" , "Brief expression of appreciation" .)