Very cheerful (6)
I believe the answer is:
blithe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very cheerful</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 blithe that I've seen before include "Shelley: 'Hail to thee . . . . . . spirit! Bird thou never wert'" , "Light-hearted and good-humoured" , "Heedless" , "Happy and maybe casual" , "Uncaring" .)