B___ filler appears wet when recycled (10)

I believe the answer is:

wastepaper

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'b filler' is the definition.
The definition suggests a singular noun which matches the answer.

'appears wet when recycled' is the wordplay.
'appears wet' can be anagrammed to 'WASTEPAPER'.
Though, I am not clear how this is indicated.

Can you help me to learn more?

(Other definitions for wastepaper that I've seen before include "Office or domestic bin" , "rubbish" .)

I've seen this clue in the Sydney Morning Herald.

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