Icy rain (4)
(Other definitions for hail that I've seen before include "Ice pellets - greeting" , "Word of greeting" , "Acclaim; frozen rain" , "Call for - praise, vociferously" , "Frozen rain or Roman greeting" .)
'icy rain' 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 "Partly melted falling snow or hail" , "Rain mixed with snow or hail" , "In foul weather" , "Partly melted falling 16 across or 18 down" , "Mixed rain and melting snow" .)