Mixture of rain and snow (5)
I believe the answer is:
sleet
'mixture of rain and snow' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sleet that I've seen before include "Cold precipitation" , "Freezing rain" , "Icy rain" , "Precipitate evolution" , "Rain mixed with snow or hail" .)