Absurd or foolish (4)
I believe the answer is:
daft
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">absurd</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">foolish</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for daft that I've seen before include "'Silly, foolish (4)'" , "'---- as a brush': dotty" , "Informally silly or foolish" , "Informally silly or crazy" , "Scatty" .)