Watson of the Harry Potter films (4)
I believe the answer is:
emma
'watson of the harry potter films' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for emma that I've seen before include "heroine of novel" , "Flaubert's heroine" , "Ack -, a term for a.m." , "Name of Nelson's Lady Hamilton" , "Girl's name - Jane Austen novel" .)