Crossword Genius

Did smoking make it sleepy? (6)

Ross

I believe the answer is:

kipper

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'it sleepy?' is the definition.
The definition suggests a singular noun which matches the answer.

I cannot understand how the rest of the clue works.

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(Other definitions for kipper that I've seen before include "has been caught napping" , "Cured or smoked herring" , "(Fishy) type of tie" , "part of breakfast?" , "One drops off" .)

I've seen this clue in the Evening Standard.
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