Crossword Genius

Unmarried sister (3)

Ross

I believe the answer is:

nun

This clue is a double definition.

'unmarried' is the first definition.
(thesaurus)

'sister' is the second definition.
(sister is a term of address for a nun)

(Other definitions for nun that I've seen before include "A palindromic lady in religious order" , "Fancy pigeon variety" , "One who's taken vows" , "Devout woman" , "eg Carmelite" .)

I've seen this clue in The Globe and Mail.
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