Deep-rooted or ingrained (10)
I believe the answer is:
inveterate
This clue is a double definition.
'deep-rooted' is the first definition.
(thesaurus)
'ingrained' is the second definition.
(thesaurus)
(Other definitions for inveterate that I've seen before include "Long-formed (bad habit)" , "Long-established" , "long-standing" , "Confirmed in (bad) habit" , "Habitual" .)