Cheerful person (8)
(Other definitions for optimist that I've seen before include "One always tends to take a favourable view of things" , "Someone with a bright and hopeful nature" , "glass half-full type?" , "One wearing rose-tinted spectacles" , "Glass-half-full person" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cheerful person</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 ray of sunshine that I've seen before include "Someone to make you smile" , "Cheerful person" , "joy to be with" , "One who makes others feel happy; beam" , "One cheering up other people" .)