Make better, improve (10)
I believe the answer is:
ameliorate
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">make better</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">improve</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for ameliorate that I've seen before include "Make (something) better" , "Make (a bad thing) better" , "Become better" , "seen to improve" .)