Drops from the sky (4)
'drops from the sky' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rain that I've seen before include "Storm" , "Wet weather" , "Precipitation" , "previous rule?" , "eg A shower" .)
(Other definitions for rains that I've seen before include "Tropical wet season" , "Comes down from cloud" , "Showers" , "Falls in droplets" .)