Sturdy, powerful (6)
I believe the answer is:
robust
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">sturdy</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">powerful</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for robust that I've seen before include "Sturdy, resilient" , "Vigorous - healthy" , "Unlikely to break" , "Strong and healthy" , "Having a strong constitution" .)