By oneself, alone (4)
I believe the answer is:
solo
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">by oneself</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">alone</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(as in a musical solo)</span><br/ ><br/ ></span>
(Other definitions for solo that I've seen before include "Unaccompanied flight" , "Han - (Star Wars); fly unaccompanied" , "Performance by one person" , "On one's own, unaccompanied" , "Go it alone" .)