Sources for elder statesman get in contact possibly underpinning a politician's greatness (9)

I believe the answer is:

ampleness

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'greatness' is the definition.
(thesaurus)

'sources for elder statesman get in contact possibly underpinning a politician's' is the wordplay.
'sources for' suggests taking the first letters (the first letters or sources of the words).
'get in' indicates putting letters inside.
'contact possibly' becomes 'lens' (I can't explain this - if you can you should believe this answer much more).
'underpinning' says to put letters next to each other (in a down clue, some letters go under others).
'politician' becomes 'MP' (Member of Parliament).
The initial letters of 'elder statesman' is 'es'.
'es' put inside 'lens' is 'leness'.
'a'+'mp'='amp'
'leness' put after 'amp' is 'AMPLENESS'.

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I've seen this clue in The Independent.

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