It indicates unsettled weather (6)
I believe the answer is:
shower
'weather' is the definition.
(I know that shower is a type of downfall)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for shower that I've seen before include "volley" , "A brief fall of rain or a cleansing spray" , "Person uncovering" , "rain not sounding the same" , "Useless people" .)