Nasty fall? (5)
I believe the answer is:
sleet
'nasty fall?' 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" , "Mixture of rain and snow" , "Partially frozen rain" , "Partly melted falling snow or hail" , "Wintry precipitation" .)