Crossword Genius

Deficiency that may presage long winter in Canada? (9)

Ross

I believe the answer is:

shortfall

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'deficiency' is the definition.
(I know that shortfall is a type of deficiency)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for shortfall that I've seen before include "Loss" , "what we're lacking" , "lack" , "Not quite what's expected" , "Deficit of something required" .)

I've seen this clue in The Times.
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