Particularly reliable source of cash among sweetshop's stock? (5,6,4)

I believe the answer is:

extra strong mint

'among sweetshop's stock?' is the definition.

'particularly reliable source of cash' is the wordplay.
'particularly' becomes 'extra' ('extra' can be a synonym of 'particularly').
'reliable' becomes 'strong'.
'source of cash' becomes 'mint' (a mint makes coins).
'extra'+'strong'+'mint'='EXTRA STRONG MINT'

I've seen this clue in The Guardian.

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