Quick or agile (5)
I believe the answer is:
nifty
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">quick</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">agile</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for nifty that I've seen before include "Stylish, nimble" , "Particularly effective; stylish" , "Stylish; agile (informal)" , "Dandy" , "Really good (slang)" .)