Mystical incantation (6)
I believe the answer is:
mantra
'mystical incantation' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mantra that I've seen before include "Sacred words used as incantation" , "Hindu word or phrase as aid to meditation" , "oft repeated stock phrase?" , "Chanted words" , "Aid to concentration (Buddhism,Hinduism)" .)