Party extremely permissive, duke's high? (5)
I believe the answer is:
doped
'high?' is the definition.
(thesaurus)
'party extremely permissive duke's' is the wordplay.
'party' becomes 'do' (do can informally mean a party).
'extremely' means to remove the middle letters (letters on the extremes of the word are used).
'duke' becomes 'd' (abbreviation).
'permissive' with its centre taken out is 'pe'.
'do'+'pe'+'d'='DOPED'
(Other definitions for doped that I've seen before include "Nobbled" , "Under the influence of narcotics" , "Drugged" .)