Clio's sister (5)
I believe the answer is:
erato
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">clio's sister</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 erato that I've seen before include "Muse of lyric poetry and mime" , "Source of poetic inspiration" , "verses she inspired" , "Clio's sister" , "Poet's inspiration" .)