Solemn observance (10)
(Other definitions for ceremonial that I've seen before include "Official" , "Ritual(istic)" , "Ritual procedure" , "Purely formal" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">solemn observance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(eg a religious rite)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rite that I've seen before include "form of service" , "Solemn ceremony" , "Ceremony - ritual" , "Ceremony, liturgy" , "something like mass" .)