Laboratory item (4,4)
I believe the answer is:
test tube
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">laboratory item</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 test tube that I've seen before include "Small glass cylinder with one end closed, used in laboratory" , "Lab equipment" , "part of an experiment" , "Laboratory experimental container" , "glass vessel" .)