Invent discourse about one spirit (9)
I believe the answer is:
originate
'invent' is the definition.
(I've seen this before)
'discourse about one spirit' is the wordplay.
'discourse' becomes 'orate' (I've seen this in another clue).
'about' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'spirit' becomes 'gin' (alcoholic spirit).
'i'+'gin'='igin'
'orate' enclosing 'igin' is 'ORIGINATE'.
(Other definitions for originate that I've seen before include "Stem" , "Set up" , "Launch" , "Come into existence" , "From kick off" .)