Girl’s name partly hidden, in actuality (4)
I believe the answer is:
nina
'girl's name' is the definition.
'partly hidden in actuality' is the wordplay.
'partly' indicates the answer is hidden within the clue (part of the clue is used).
'NINA' is hidden in the letters of 'hidden in actuality'.
(Other definitions for nina that I've seen before include "Al Hirschfeld's 'hidden' daughter" , "Girl" , "hidden crossword message" , "- Simone, US singer" , "- - Simone, 1933-2003, singer" .)