Crossword Genius

Instance of longevity, diagnosing no upsets (1,4,7)

Ross

I believe the answer is:

a good innings

I'm a little stuck... Click here to teach me more about this clue!

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

'diagnosing no upsets' is the wordplay.
'upsets' indicates anagramming the letters.
'diagnosing'+'no'='diagnosingno'
'diagnosingno' with letters rearranged gives 'A GOOD INNINGS'.

Can you help me to learn more?

I've seen this clue in The Everyman puzzle in The Observer.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.