Long-established custom (9)
I believe the answer is:
tradition
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">long-established custom</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tradition that I've seen before include "Long-established custom or belief" , "Practice of long standing" , "Transmitted customs" , "Customs etc handed down" , "Established custom" .)