H, to Hera (3)
I believe the answer is:
eta
'h to hera' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eta that I've seen before include "letter from Greece?" , "Letter from Doris" , "Greek letter - Basque nationalist movement" , "Militant Basque organisation - Greek letter" , "Something like 10 [RHO]" .)