1492 ship
I believe the answer is:
'1492 ship' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nina that I've seen before include "One of Columbus's ships in 1492; girl's name" , "- - Simone, 1933-2003, singer" , "Girl" , "hidden crossword message" , "- Simone, US singer" .)