Magnifying instrument (10)
I believe the answer is:
microscope
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">magnifying instrument</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for microscope that I've seen before include "Optical magnifier" , "Optical instrument" , "Magnifying instrument" , "Tiny organisms viewer" , "Magnifying device" .)