Siren never having time for leading lady (7)

I believe the answer is:

empress

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'leading lady' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for empress that I've seen before include "1 across was from 1877" , "She rules a vast realm" , "one married to ruler?" , "Victoria, the > female penguin?" , "Female ruler" .)

I've seen this clue in The Sun.

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