Whines about playing sidekicks (7)

I believe the answer is:

cronies

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'sidekicks' is the definition.
(I know this)

'whines about playing' is the wordplay.
'whines' becomes 'cries' (I can't explain this - if you can you should believe this answer much more).
'about' means one lot of letters goes inside another.
'playing' becomes 'on' (on can mean playing or performing).
'cries' placed around 'on' is 'CRONIES'.

Can you help me to learn more?

(Another definition for cronies that I've seen is " 'Buddies, sidekicks (7)'".)

I've seen this clue in The Telegraph.

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