Seer will utterly make money! (7)
I believe the answer is:
prophet
'seer' is the definition.
(I know that prophet is a type of diviner)
'utterly make money' is the wordplay.
'utterly' shows a homophone (sound like) (as uttered).
'make money' becomes 'profit' (I've seen this in another clue).
'profit' is a homophone of 'PROPHET'.
'will' is the link.
(Other definitions for prophet that I've seen before include "One speaks by divine inspiration" , "Moses, for example" , "Divine spokesman or forecaster" , "Soothsayer" , "One who anticipates" .)