Old nationalist boycotts strike, run internally (10)

I believe the answer is:

blackshirt

'old nationalist' is the definition.
(Mussolini's fascists were called blackshirts)

'boycotts strike run internally' is the wordplay.
'boycotts' becomes 'blacks' (black lists).
'strike' becomes 'hit' (synonyms).
'run' becomes 'r' (cricket abbreviation).
'internally' means one lot of letters goes inside another.
'hit' placed around 'r' is 'hirt'.
'blacks'+'hirt'='BLACKSHIRT'

I've seen this clue in The Times.

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