Nun or nurse? (6)
I believe the answer is:
sister
I believe this clue is a double definition.
'nun' is the first definition.
(a nun might be called sister)
'nurse?' is the second definition.
(a female nurse might be called sister)
(Other definitions for sister that I've seen before include "Tender" , "Nurse, nun and sibling" , "Close relation" , "Nun's title" , "'Nurse, nun or relative (6)'" .)