His earnest carousing may suggest this (10)

I believe the answer is:

heartiness

'suggest this' is the definition.
The definition suggests a singular noun which matches the answer.

'his earnest carousing' is the wordplay.
'his earnest' anagrams to 'HEARTINESS'.
Though, I'm not clear how this is indicated.

'may' is the link.

(Another definition for heartiness that I've seen is " cordiality".)

I've seen this clue in The Times.

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