An unpopular American in a jacket (6)

I believe the answer is:

jerkin

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'a jacket' is the definition.
(I know that jerkin is a type of jacket)

'an unpopular american in' is the wordplay.
'an unpopular american' becomes 'jerk' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'jerk'+'in'='JERKIN'

Can you help me to learn more?

(Other definitions for jerkin that I've seen before include "Leatherjacket" , "Tight, sleeveless, collarless jacket" , "Sleveless jacket" , "sort of jacket" , "sleeveless garment" .)

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

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