Be important (6)
I believe the answer is:
matter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be important</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 matter that I've seen before include "It occupies space, unlike mind or spirit" , "Substance; be important" , "Subject; be important" , "Carry weight" , "It occupies space, has substance" .)