Prognosticate (8)
I believe the answer is:
foretell
'prognosticate' is the definition.
(I know that prognosticate can be written as foretell)
This is the entire clue.
(Other definitions for foretell that I've seen before include "supporting English archer" , "Foreshadow or presage" , "'Predict, prophesy (8)'" , "Divine" , "Prognosticate" .)