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Pop padding novel summary with many, many pages (5,4)

Ross

I believe the answer is:

cream soda

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'pop' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

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(Other definitions for cream soda that I've seen before include "Vanilla-flavoured fizzy drink" , "Carbonated soft drink" , "Vanilla-flavoured pop" , "Sparkling stuff" .)

I've seen this clue in The Times.
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