Crossword Genius

To us, Rosie getting upset is no laughing matter (7)

Ross

I believe the answer is:

serious

'no laughing matter' is the definition.
(thesaurus)

'to us rosie getting upset' is the wordplay.
'getting upset' indicates an anagram.
'us'+'rosie'='usrosie'
'usrosie' with letters rearranged gives 'SERIOUS'.

'is' is the link.

(Other definitions for serious that I've seen before include "Earnest - important" , "Important - solemn" , "Stern" , "Important -- grave" , "Solemn, thoughtful" .)

I've seen this clue in the Evening Standard.
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