Upset with vegetables I had rejected (6)
I believe the answer is:
dismay
'upset' is the definition.
(dismay can mean to upset)
'with vegetables i had rejected' is the wordplay.
'with' is a charade indicator (letters next to each other).
'vegetables' becomes 'yams' (yam is a kind of vegetable).
'i had' becomes 'I'd' (I'd).
'rejected' is a reversal indicator.
'yams' next to 'id' is 'yamsid'.
'yamsid' written backwards gives 'DISMAY'.
(Other definitions for dismay that I've seen before include "Fill with apprehension" , "trouble" , "Affright" , "Consternation, distress" , "Consternation, disheartenment" .)