Sudden flood of light material (6)

I believe the answer is:

inrush

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'sudden flood' is the definition.
'inrush' can be an answer for 'flood' (I've seen this in another clue). I am unsure of the 'sudden' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for inrush that I've seen before include "Sudden flow inwards" , "hasty entrance" , "Crowd invasion" , "Sudden inward flow" , "Sudden surge" .)

I've seen this clue in The Globe and Mail.

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