Crossword Genius

Nell, evidently fast mistress (7)

Ross

I believe the answer is:

quickly

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'nell evidently' is the definition.
I can't judge whether this definition defines the answer.

'fast mistress' is the wordplay.
'fast' becomes 'quick' (similar in meaning).
'mistress' becomes 'ly' (I am not sure about this - if you are sure you should believe this answer much more).
'quick'+'ly'='QUICKLY'

Can you help me to learn more?

(Other definitions for quickly that I've seen before include "Speedily" , "Rapidly; promptly" , "Mistress of Eastcheap tavern" , "At speed" .)

I've seen this clue in the Evening Standard.
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