Nostradamus, supposedly (4)
I believe the answer is:
seer
'nostradamus supposedly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for seer that I've seen before include "One having visions of the future" , "Person who can read the future" , "Prophet or clairvoyant" , "Person with unusual powers of foresight" , "Soothsayer" .)