Box opener of myth (7)
I believe the answer is:
pandora
'box opener of myth' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pandora that I've seen before include "Adrian Mole's love; box-of-troubles girl" , "Her box was filled with all the ills of the world" , "Possessor of famous box" , "In Greek myth, the first woman with disastrous Box" , "Her mythical box was filled with evil" .)