Pass out leaving very little impression (5)

I believe the answer is:

faint

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'pass out' is the definition.
(fainting is a kind of passing out)

I don't understand how the remainder of the clue works.

(Other definitions for faint that I've seen before include "dull" , "Swoon - pale" , "hard to hear" , "feeble" , "Hard to see" .)

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

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