Crossword Genius

Reserve to give penalty during a game (4)

Ross

I believe the answer is:

book

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'reserve' is the definition.
(to book something is to reserve it)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for book that I've seen before include "strict regulations" , "Volume - maybe thrown at offender" , "thing that shouldn't be cooked?" , "See 1 ac" , "Reserve; tome" .)

I've seen this clue in The Irish Times.
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