Upsetting but rewarding service (7)

I believe the answer is:

tipping

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

'rewarding service' is the definition.
(I've seen this before)

'upsetting but' is the wordplay.
'upsetting' becomes 'tip' (to tip something is to upset it).
'but' becomes 'ping' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tip'+'ping'='TIPPING'

Can you help me to learn more?

(Other definitions for tipping that I've seen before include "Giving a gratuity" , "Rewarding service" .)

I've seen this clue in The Times.

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.