Recording gangster, capturing most of his ultimately immoral youth (9)
I believe the answer is:
childhood
'ultimately immoral youth' is the definition.
'childhood' can be an answer for 'youth' (thesaurus). I'm not sure about the 'ultimately immoral' bit.
'recording gangster capturing most of his' is the wordplay.
'recording' becomes 'cd' (CD is an example).
'gangster' becomes 'hood' (I've seen this before).
'capturing' is an insertion indicator.
'most of his' becomes 'hil' (I can't justify this - if you can you should give a lot more credence to this answer).
'cd'+'hood'='cdhood'
'cdhood' going around 'hil' is 'CHILDHOOD'.
Can you help me to learn more?
(Other definitions for childhood that I've seen before include "Between infancy and adolescence" , "Minority" , "Immature state" , "Time of immaturity" , "Young state" .)