Optimistic, buoyant (6)
I believe the answer is:
upbeat
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">optimistic</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">buoyant</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for upbeat that I've seen before include "Promising" , "Conductor's beginning" , "Cheerful and encouraging, like lively music" , "Of mood, cheerful and optimistic" , "Cheerfully optimistic" .)