Family bank Spooner dismissed as stupid and silly (3,3,3)

I believe the answer is:

mum and dad

'family bank' is the definition.
('the bank of mum and dad')

'spooner dismissed as stupid and silly' is the wordplay.
I cannot quite see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is located in the answer.
'silly' could be 'mad' and 'mad' is present in the remaining letters.
This explanation may well be incorrect...

(Another definition for mum and dad that I've seen is " (My) parents".)

I've seen this clue in The Guardian.

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