Beat discrimination with a change of leader (5)

I believe the answer is:

baste

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'beat' is the definition.
(I know that baste is a more specific form of the action beat)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for baste that I've seen before include "Keep moist" , "Beast (anag.)" , "Sew" , "Looking at with interest" , "Moisten (a roast)" .)

I've seen this clue in The Independent.

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