Luminary on a spree, stupidly consuming gallons (9)
I believe the answer is:
personage
'luminary' is the definition.
(I've seen this before)
'on a spree stupidly consuming gallons' is the wordplay.
'stupidly' indicates anagramming the letters.
'consuming' indicates putting letters inside.
'gallons' becomes 'g'.
'on'+'a'+'spree'='onaspree'
'onaspree' anagrammed gives 'personae'.
'personae' enclosing 'g' is 'PERSONAGE'.
(Other definitions for personage that I've seen before include "big noise, it's said" , "VIP" , "Somebody" , "(Important) individual" , "Luminary" .)