Be aware of (4)
I believe the answer is:
know
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be aware 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 know that I've seen before include "Be acquainted with" , "Be familiar with" , "Be dangerously well informed" , "A Channel port, type of sole" , "Have information" .)