Based on fact (4)
I believe the answer is:
true
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">based on fact</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for true that I've seen before include "In accordance with facts" , "Real; accurate" , "Exact; faithful" , "Veracious" , "to be believed?" .)