Sting's opening for Simon & Garfunkel, maybe after millions (5)

I believe the answer is:

smart

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

I can't explain the rest of the clue.

(Other definitions for smart that I've seen before include "Sting - witty" , "Clean, tidy; clever" , "Clever - feel mild pain" , "Rankle; trim" , "Sort of card" .)

I've seen this clue in The Independent.

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