Incorrigible drunken teenager ruined with no ID (12)
I believe the answer is:
unregenerate
'incorrigible' is the definition.
('unregenerate' can be similar in meaning to 'incorrigible')
'drunken teenager ruined with no id' is the wordplay.
'drunken' is an anagram indicator.
'with no' indicates named letters should be taken away.
'teenager'+'ruined'='teenagerruined'
'teenagerruined' with 'id' removed is 'teenagerrune'.
'teenagerrune' with letters rearranged gives 'UNREGENERATE'.
(Other definitions for unregenerate that I've seen before include "Not reforming or repenting" , "stubborn and bad" , "Obstinately bad" , "Not showing repentance" .)