Test or put to experimental use (3,3)
I believe the answer is:
try out
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">test</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(try out can mean to test or trial)</span><br/ ><br/ >'<span class="explanation-format__original">put to experimental use</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for try out that I've seen before include "Sample" , "Taste" , "Test and evaluate" , "Put to experimental use" .)