Socialist men upset with partisanship (12)

I believe the answer is:

sectionalism

'partisanship' is the definition.
(sectionalism is a kind of partisanship)

'socialist men upset' is the wordplay.
'upset' indicates an anagram.
'socialist'+'men'='socialistmen'
'socialistmen' with letters rearranged gives 'SECTIONALISM'.

'with' acts as a link.

I've seen this clue in The Hindu.

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