Fortuneteller (6)
'fortuneteller' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for seer that I've seen before include "Oracle or clairvoyant" , "Person of vision" , "Sage with 20ac" , "Oracle or prophet" , "One having visions of the future" .)
(Other definitions for mystic that I've seen before include "Otherworldly" , "Believer in truths beyond tangible proof" , "Relating to occult rites" , "Spiritualist" , "Allegorical; sacredly obscure" .)