I'm not joking very much (9)

I believe the answer is:

seriously

I believe this is a double definition.

'i'm not joking' is the first definition.
(I'm being serious)

'very much' is the second definition.
(seriously can mean to a great degree)

(Other definitions for seriously that I've seen before include "In a solemn and thoughtful manner" , "Gravely" .)

I've seen this clue in The Times.

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