More important (6)
I believe the answer is:
bigger
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">more important</span>' is the definition.<br/ ><span class="explanation-format__explanation">('big' can be similar in meaning to 'important')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bigger that I've seen before include "Greater in size" , "louder" , "Larger" , "Comparatively huge" .)