Issue that's upset girl (5)
I believe the answer is:
susie
'girl' is the definition.
'issue that's upset' is the wordplay.
'that's upset' is an anagram indicator.
'issue' anagrammed gives 'SUSIE'.
(Other definitions for susie that I've seen before include "Wake Up Little - (Everly Brothers)" , "Tongue-twister sister sewing shirts for soldiers" , "Woman" , "Old song: ''If you knew . . . . . like I know . . . . .''" , "Girl's name" .)