Female with a nice new boyfriend (6)
I believe the answer is:
fiance
'boyfriend' is the definition.
(thesaurus)
'female with a nice new' is the wordplay.
'female' becomes 'f' (abbreviation).
'with' indicates putting letters inside.
'new' indicates an anagram.
'nice' with letters rearranged gives 'ince'.
'a' placed into 'ince' is 'iance'.
'f'+'iance'='FIANCE'
(Other definitions for fiance that I've seen before include "One waiting to go to match" , "He's going to marry" , "Groom-to-be" , "One who's engaged" , "One getting married" .)