Newspapers cover a long period in forecasts (8)
I believe the answer is:
presages
'forecasts' is the definition.
('presage' can be a synonym of 'forecast')
'newspapers cover a long period' is the wordplay.
'newspapers' becomes 'press' (the press is the newspaper industry).
'cover' means one lot of letters goes inside another.
'a long period' becomes 'age' (I've seen this in another clue).
'press' placed around 'age' is 'PRESAGES'.
'in' is the link.
(Other definitions for presages that I've seen before include "Augurs, bodes" , "Foreshadows, is advance sign of" , "Foreshadows in press age" , "Forecasts" .)