Unexpected advantages when the gale subsides (9)

I believe the answer is:

windfalls

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'unexpected advantages' is the definition.
Although both the answer and definition are plural nouns, I cannot understand how they can define each other.

'the gale subsides' is the wordplay.
'the gale' becomes 'wind' (I've seen this in another clue).
'subsides' becomes 'falls' (I can't justify this - if you can you should believe this answer much more).
'wind'+'falls'='WINDFALLS'

'when' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Independent.

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