Nationalist nuts letting in posh artist, allowing citizenship (14)

I believe the answer is:

naturalisation

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'citizenship' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'nationalist nuts letting in posh artist' is the wordplay.
'nuts' indicates an anagram (nuts can mean crazy).
'letting in' indicates putting letters inside.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'nationalist' with letters rearranged gives 'natlisation'.
'u'+'ra'='ura'
'natlisation' placed around 'ura' is 'NATURALISATION'.

'allowing' is the link.

Can you help me to learn more?

I've seen this clue in The Telegraph.

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