Shrink, which is a snag (8)

I believe the answer is:

drawback

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'snag' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for drawback that I've seen before include "Fly in the ointment" , "Catch" , "Obstacle" , "Disadvantage, problem" , "Hindrance - disadvantage" .)

I've seen this clue in the Evening Standard.

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