Gem set by itself
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gem set by itself</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for solitaire that I've seen before include "Patience game" , "thrush" , "Board game played by one person" , "[PATIENCE], especially in America" , "songbird" .)