Roald Dahl heroine
I believe the answer is:
'roald dahl heroine' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for matilda that I've seen before include "Girl's name (she goes waltzing!)" , "would go around with a swagger" , "one celebrated down under" , "Waltzing girl" , "She waltzes in Australian song" .)