You were lying when you said you were evaluating it (8)

I believe the answer is:

mattress

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

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(Other definitions for mattress that I've seen before include "Large thick pad on the bed" , "Soft part of bed" , "Sleeping support" , "Palliasse" , "It could be slept on" .)

I've seen this clue in the Evening Standard.

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