But it doesn't upset the recipient! (3)
I believe the answer is:
tip
'upset the recipient' is the definition.
'tip' can be an answer for 'upset' (I've seen this in another clue). I'm not sure about the 'the recipient' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tip that I've seen before include "for writers, it may be felt" , "End; piece of advice" , "End; overbalance" , "single piece of asparagus, perhaps" , "Topple over - hint" .)