My Zoom employee evaluation: "Jolly at first, then all upset" (4)

I believe the answer is:

jeez

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

'my zoom employee evaluation' is the definition.
I can't tell whether this defines the answer.

'jolly at first then all upset' is the wordplay.
'at first' indicates taking the first letters.
'then all' becomes 'zee' (I can't justify this - if you can you should give a lot more credence to this answer).
'upset' is a reversal indicator.
The first letter of 'jolly' is 'j'.
'zee' reversed gives 'eez'.
'j'+'eez'='JEEZ'

Can you help me to learn more?

I've seen this clue in The Independent.

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.