Realise (4)
I believe the answer is:
know
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">realise</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that know is a type of realise)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for know that I've seen before include "Be familiar with" , "Articulated" , "Recognise" , "Be acquainted with" , "Be sure of something" .)