Left one in Capitol unusually attached to party (9)

I believe the answer is:

political

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'attached to party' is the definition.
I know that 'party' relates to this answer.

'left one in capitol unusually' is the wordplay.
'left' becomes 'l' (common abbreviation).
'one' becomes 'i' (Roman numeral).
'in' indicates putting letters inside.
'unusually' is an anagram indicator.
'l'+'i'='li'
'capitol' anagrammed gives 'potical'.
'li' put into 'potical' is 'POLITICAL'.

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(Other definitions for political that I've seen before include "Involved with affairs of state" , "for parties?" , "Governmental" .)

I've seen this clue in The Times.

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