Island group getting central points in arguments (9)

I believe the answer is:

keystones

'central points in arguments' is the definition.
(basic points or principles of an argument)

'island group getting' is the wordplay.
'island' becomes 'key ' (I've seen this before).
'group' becomes 'stones' (the Rolling Stones).
'getting' is a charade indicator (letters next to each other).
'key'+'stones'='KEYSTONES'

(Another definition for keystones that I've seen is " They are central to arches".)

I've seen this clue in The Telegraph.

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