Youngster's prize books removed (3)

I believe the answer is:

boy

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'youngster's' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for boy that I've seen before include "SECOND HALF OF 14" , "Young male" , "Male child" , "Son" , "Lad" .)

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