When marked down it's not cheap (7)

I believe the answer is:

cushion

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'when marked down' is the definition.
'cushion' can be an answer for 'down' (thesaurus). I am unsure of the 'when marked' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for cushion that I've seen before include "Part of a billiard table" , "Dampen" , "Buffer" , "Soft pad, of feathers say" , "absorb shock?" .)

I've seen this clue in The Globe and Mail.

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