Notice registered prophet (4)
I believe the answer is:
seer
'prophet' is the definition.
(both can mean someone who tells the future)
'notice registered' is the wordplay.
'notice' becomes 'see' (notice can mean to spot or see).
'registered' becomes 'R' (abbreviation, as in registered trademark).
'see'+'r'='SEER'
(Other definitions for seer that I've seen before include "Sage with 20ac" , "Person who can read the future" , "Oracle or clairvoyant" , "Distinguishing quality" , "One fortelling future" .)