Systematic investigation (8)
I believe the answer is:
research
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">systematic investigation</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 research that I've seen before include "Investigation designed to expand knowledge" , "What may make you a doctor" , "Look into" , "enquiry" , "Fact-finding" .)