Greeting that comes from above (4)

I believe the answer is:

hail

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'greeting' is the definition.
('hail' is a greeting)

I don't understand the rest of the clue.

(Other definitions for hail that I've seen before include "Shower of ice pellets" , "Stones from the sky" , "Greeting - falling stones" , "Greet; frozen rain" , "Greet loudly" .)

I've seen this clue in The Times.

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