Crossword Genius

Turn out too informally beneath gown (10)

Ross

I believe the answer is:

underdress

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'turn out too informally' is the definition.
I can't tell whether this definition defines the answer.

'beneath gown' is the wordplay.
'beneath' becomes 'under' (under means beneath or underneath).
'gown' becomes 'dress' (gown is a kind of dress).
'under'+'dress'='UNDERDRESS'

Can you help me to learn more?

(Another definition for underdress that I've seen is " pants?".)

I've seen this clue in The Daily Express.
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