Sappho's Muse (5)
I believe the answer is:
'sappho's muse' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for erato that I've seen before include "daughter of Zeus" , "Poetic Muse ; eighteen (anag.)" , "Muse of lyric poetry and mime" , "Poet's inspiration" , "One inspiring" .)