Practice of long standing (9)
I believe the answer is:
tradition
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">practice of long standing</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tradition that I've seen before include "Body of beliefs and customs handed down through generations" , "Custom, long-standing practice" , "Transmitted customs" , "Inherited custom" , "Custom passed on" .)