Leading lady and heir one upset (7)
I believe the answer is:
heroine
'leading lady' is the definition.
(I've seen this in another clue)
'heir one upset' is the wordplay.
'upset' is an anagram indicator.
'heir'+'one'='heirone'
'heirone' with letters rearranged gives 'HEROINE'.
'and' is the link.
(Other definitions for heroine that I've seen before include "Leading lady" , "Woman of outstanding courage" , "Intrepid woman" , "Chief female character in a book" , "Woman of courageous achievements" .)