Fines inn holding messy All-Ireland party? (4,4)

I believe the answer is:

sinn fein

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'party?' is the definition.
(Irish political party)

'fines inn holding messy all-ireland' is the wordplay.
'fines inn' can be anagrammed to 'SINN FEIN'.
Though, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for sinn fein that I've seen before include "Irish political movement" , "Fine inns (anag.)" , "Political party to be found in fine inns" , "Irish nationalist party" , "GerryAdams's political party" .)

I've seen this clue in The Irish Times.

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