Wet weather? Down with it! (4)

I believe the answer is:

pour

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'down with it' is the definition.
'pour' can be an answer for 'down' ('pour down' can be a synonym of 'down'). I'm unsure of the 'with it' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for pour that I've seen before include "to drop, when it's heavy" , "Give out liquid" , "Teem" , "Cause to flow as from pot to cup" , "Tip liquid from container" .)

I've seen this clue in the Evening Standard.

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