Service gratuity (3)

I believe the answer is:

tip

I believe this is a double definition.

'service' is the first definition.
(service charge)

'gratuity' is the second definition.
(as in a gratuity to a waiter)

(Other definitions for tip that I've seen before include "Give the likely winner for gratuity" , "tiny reward" , "Gratuity; hint" , "present!" , "End - pourboire" .)

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

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