Queen at Olympus, originally a goddess (5)
I believe the answer is:
erato
'a goddess' is the definition.
(thesaurus)
'queen at olympus originally' is the wordplay.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'originally' suggests taking the first letters.
The first letter of 'olympus' is 'o'.
'er'+'at'+'o'='ERATO'
(Other definitions for erato that I've seen before include "Clio's sister" , "Muse of 11 and 23" , "Muse of lyric poetry and mime" , "Poet's muse" , "One inspiring" .)