Negligent about young woman (6)
I believe the answer is:
remiss
'negligent' is the definition.
(similar in meaning)
'about young woman' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'young woman' becomes 'miss' (title for a young woman).
're'+'miss'='REMISS'
(Other definitions for remiss that I've seen before include "Negligent like misers" , "Failing in what duty requires" , "Wrong" , "At fault" , "Careless concerning a girl?" .)