Sinatra does a turn for the Russian empress (7)
I believe the answer is:
tsarina
'russian empress' is the definition.
(I've seen this before)
'sinatra does a turn for the' is the wordplay.
'sinatra does' becomes 'sari' (I can't explain this - if you can you should give a lot more credence to this answer).
'a' becomes 'an'.
'turn' says the letters should be written in reverse.
'for' says to put letters next to each other (I've seen this in other clues).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'an' reversed gives 'na'.
'sari'+'na'='sarina'
'sarina' put after 't' is 'TSARINA'.
Can you help me to learn more?
(Other definitions for tsarina that I've seen before include "Wife of an old Russian emperor" , "top Russian women" , "Russian noblewoman" , "Russian empress (S, not Z)" , "Catherine, say" .)