Weather to turn rainy in the end (5)
I believe the answer is:
windy
'weather' is the definition.
(as in windy weather)
'turn rainy in the end' is the wordplay.
I cannot really understand how this works, but
'turn' could be 'wind' (I've seen this in another clue) and 'wind' is present in the answer.
A single letter 'y' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'to' is the link.
(Other definitions for windy that I've seen before include "Chicago, the _____ City" , "Breezy" , "Conceited - nervous - registering on the Beaufort scale" , "Frightened - not still" , "The sort of weather" .)