Girl getting all upset about nothing (4)
I believe the answer is:
lola
'girl' is the definition.
'all upset about nothing' is the wordplay.
'upset' says the letters should be written in reverse.
'about' means one lot of letters goes inside another.
'nothing' becomes 'O' (looks like zero - 0).
'all' written backwards gives 'lla'.
'lla' placed around 'o' is 'LOLA'.
'getting' acts as a link.
(Other definitions for lola that I've seen before include "Whatever -- wants (song); -- Montez, mistress of Ludwig I" , "song by 4 [THE KINKS]" .)