Answer: tipping

AnswerCrossword Clue
TIPPINGAdding 15 for the waiter, say%
tippingColor (something) at its end or edge
tippingAttach to or cover the end or extremity of
tipping(in bookbinding) Paste a single page, typically an illustration, to the neighboring page of a book by a thin line of paste down its inner margin
tippingarticulating with the tongue