Very powerful (6)
I believe the answer is:
mighty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very powerful</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mighty that I've seen before include "Powerful - huge" , "Having great strength" , "Large" , "Very powerful/strong" , "Extremely" .)