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