Book of religious songs (6)
I believe the answer is:
hymnal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">book of religious songs</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 hymnal that I've seen before include "chorister's guide" , "Book of church music" , "Religious songbook" , "Book found in church" , "Church song book" .)