Portable seat in an American saloon (5)

I believe the answer is:

sedan

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'american saloon' is the definition.
(US term for a saloon car)

'portable seat in an' is the wordplay.
'portable seat in' becomes 'sed' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sed'+'an'='SEDAN'

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(Other definitions for sedan that I've seen before include "Chair to be carried by two" , "Saloon car (US)" , "Type of chair - battle" , "Four-door car" , "Old carrier chair for Danes" .)

I've seen this clue in the Evening Standard.

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