Singularity (7)
I believe the answer is:
oneness
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">singularity</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 oneness that I've seen before include "single state" , "Unity" , "Singular state" , "singularity" , "Singular quality" .)