Diminutive American's letter to a former spouse (3)

I believe the answer is:

tex

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'diminutive american's' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'letter to a former spouse' is the wordplay.
'letter' becomes 't' ().
'to a former spouse' becomes 'ex' (an ex-spouse).
't'+'ex'='TEX'

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(Another definition for tex that I've seen is " Southern American (abbrev.)".)

I've seen this clue in the Evening Standard.

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