Ring after ring, unusually mounted as exclusive set (2-5)

I believe the answer is:

in-group

'exclusive set' is the definition.
(I've seen this before)

'ring after ring unusually mounted' is the wordplay.
'ring' becomes 'o'.
'after' is a charade indicator (letters next to each other).
'unusually' indicates an anagram.
'mounted' becomes 'up' (I've seen this in other clues**).
'ring' anagrammed gives 'ingr'.
'o' put after 'ingr' is 'ingro'.
'ingro'+'up'='IN-GROUP'

'as' is the link.

(Another definition for in-group that I've seen is " Exclusive set".)

I've seen this clue in The Telegraph.

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