High plane, the jumbo (8)
I believe the answer is:
elephant
'jumbo' is the definition.
(thesaurus)
'high plane the' is the wordplay.
'high' is an anagram indicator (can mean drunk or on drugs and hence disordered).
'plane'+'the'='planethe'
'planethe' anagrammed gives 'ELEPHANT'.
(Other definitions for elephant that I've seen before include "The animal that never forgets" , "Huge mammal" , "Large land mammal" , "Jumbo" , "bigger one from two continents?" .)