Tesla possibly included in Joy's promotion (9)
I believe the answer is:
elevation
'promotion' is the definition.
(I've seen this before)
'tesla possibly included in joy's' is the wordplay.
'tesla possibly' becomes 'ev' (I can't explain this - if you can you should believe this answer much more).
'included in' indicates putting letters inside.
'joy' becomes 'elation' (elation is a kind of joy).
'ev' placed into 'elation' is 'ELEVATION'.
Can you help me to learn more?
(Other definitions for elevation that I've seen before include "High point" , "Drawing of the external face of a building" , "Height above a given level" , "Height - a live note (anag)" , "Diagram" .)