Academic drunk cautioned by US city when reversing (11)
I believe the answer is:
educational
'academic' is the definition.
(thesaurus)
'drunk cautioned by us city when reversing' is the wordplay.
'drunk' indicates an anagram.
'by' is a charade indicator (letters next to each other).
'us city' becomes 'la'.
'when reversing' says the letters should be written in reverse.
'la' in reverse letter order is 'al'.
'cautioned' is an anagram of 'education'.
'education'+'al'='EDUCATIONAL'
(Other definitions for educational that I've seen before include "Didactic" , "Providing knowledge" , "Relating to teaching" , "A docile aunt (anag) - instructive" , "Academic" .)