It's no joke Rosie getting upset with us (7)

I believe the answer is:

serious

'it's no joke' is the definition.
(thesaurus)

'rosie getting upset with us' is the wordplay.
'getting upset with' indicates an anagram.
'rosie' anagrammed with 'us' makes 'SERIOUS'.

(Other definitions for serious that I've seen before include "Stern" , "Not light or frivolous" , "Earnest; vital" , "Earnest, sincere" , "Important - solemn" .)

I've seen this clue in The Globe and Mail.

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