Levelling-off period for sheet metal (7)

I believe the answer is:

plateau

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'levelling-off period' is the definition.
I can't judge whether this definition defines the answer.

'sheet metal' is the wordplay.
'sheet' becomes 'plate' (plate is a kind of sheet).
'metal' becomes 'au' (Au is an example).
'plate'+'au'='PLATEAU'

'for' acts as a link.

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(Other definitions for plateau that I've seen before include "Elevated flatland" , "somewhere flatter?" , "Area of flat, high ground" , "Large level tract of elevated land" , "level part of range" .)

I've seen this clue in The Daily Express.

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