Promotion leads to envy veiled in delight (9)
I believe the answer is:
elevation
'promotion' is the definition.
(I've seen this before)
'leads to envy veiled in delight' is the wordplay.
'leads to' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'delight' becomes 'elation' (I've seen this before).
The first letters of 'envy veiled' is 'ev'.
'ev' inserted within 'elation' is 'ELEVATION'.
(Other definitions for elevation that I've seen before include "Height above a given level" , "Side of a building; height" , "Height above sea level" , "Leave it on for altitude of a place" , "Diagram" .)