Crossword Genius

Carroll's second Mad Hatter, essentially (7)

Ross

I believe the answer is:

atheart

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'essentially' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'carroll's second mad hatter' is the wordplay.
'carroll's second' becomes 'a' (2nd letter of 'carroll').
'mad' indicates anagramming the letters.
'hatter' with letters rearranged gives 'theart'.
'a'+'theart'='ATHEART'

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I've seen this clue in The Daily Express.
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