Prayer-book (6)
I believe the answer is:
missal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">prayer-book</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 missal that I've seen before include "Service-book" , "Book used at Catholic mass" , "book needed to get through service" , "Book of texts for the Catholic Mass" , "Catholic service book" .)