A note describing scoundrel in gallery (6)

I believe the answer is:

arcade

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'gallery' is the definition.
(I've seen this before)

'a note describing scoundrel in' is the wordplay.
'note' becomes 're' (as in do-re-mi).
'describing scoundrel' becomes 'cad' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
're' enclosing 'cad' is 'rcade'.
'a'+'rcade'='ARCADE'

Can you help me to learn more?

(Other definitions for arcade that I've seen before include "Here one may find shops" , "shopping precinct" , "covered avenue of shops" , "shopping area" , "Shopping passage" .)

I've seen this clue in The Telegraph.

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