Guru confused after a forecast (5)
I believe the answer is:
augur
'forecast' is the definition.
(I know that forecast can be written as augur)
'guru confused after a' is the wordplay.
'confused' indicates anagramming the letters.
'after' says to put letters next to each other.
'guru' with letters rearranged gives 'ugur'.
'ugur' put after 'a' is 'AUGUR'.
(Other definitions for augur that I've seen before include "Roman diviner" , "Presage, foretell" , "Bode; soothsayer" , "Prophet, forecaster" , "Presage, portend" .)