Nancy's son importing American firearms (6)

I believe the answer is:

fusils

'firearms' is the definition.
(fusil is a kind of firearm)

'nancy's son importing american' is the wordplay.
'nancy's son' becomes 'fils' ('son' in French - Nancy is a French city).
'importing' indicates putting letters inside.
'american' becomes 'us' (abbreviation for United States).
'fils' placed around 'us' is 'FUSILS'.

I've seen this clue in The Times.

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