Fallen star inside a Russian empress (7)
I believe the answer is:
tsarina
'russian empress' is the definition.
(I've seen this in another clue)
'fallen star inside a' is the wordplay.
'fallen' indicates anagramming the letters.
'inside' becomes 'in'.
'star' anagrammed gives 'tsar'.
'tsar'+'in'+'a'='TSARINA'
(Other definitions for tsarina that I've seen before include "Nicholas's wife" , "queen" , "lady of some importance" , "Wife of a tsar" , "Wife of former Russian ruler" .)