Patronizing trickster was on the way down (13)
I believe the answer is:
condescending
'patronizing trickster' is the definition.
'condescending' can be an answer for 'patronizing' (thesaurus). I'm not certain of the 'trickster' bit.
'on the way down' is the wordplay.
'on the way' becomes 'con' (I can't explain this - if you can you should believe this answer much more).
'down' becomes 'descending' (similar in meaning).
'con'+'descending'='CONDESCENDING'
'was' is the link.
Can you help me to learn more?
(Other definitions for condescending that I've seen before include "Showing (to others) that one feels superior" , "Toffee-nosed" , "Disdainful" , "Snooty" , "Offensively patronising" .)