Confirm truth of (6)
I believe the answer is:
verify
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">confirm truth of</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 verify that I've seen before include "Authenticate" , "Establish truth or accuracy of" , "Prove to be true" , "Check (facts)" , "Check to be true" .)