Reading supplements (7)
I believe the answer is:
addenda
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">reading supplements</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for addenda that I've seen before include "Codicils, riders or supplements" , "Items added to a text" , "Things added to the end of books" , "Postscripts, supplements" , "number of supplements" .)