Not just think (4)
I believe the answer is:
know
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not just think</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for know that I've seen before include "Be sure of something" , "Be dangerously well informed" , "Ken" , "Be familiar with" , "Be acquainted with" .)