Behaviour of enamoured drunk (9)
I believe the answer is:
demeanour
'behaviour' is the definition.
(synonyms)
'enamoured drunk' is the wordplay.
'drunk' indicates anagramming the letters.
'enamoured' is an anagram of 'DEMEANOUR'.
'of' acts as a link.
(Other definitions for demeanour that I've seen before include "Look" , "Behaviour" , "Enamoured of the way a person behaves" , "Outward bearing" , "Conduct" .)