Leaf of a book (4)
I believe the answer is:
page
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">leaf of a book</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 page that I've seen before include "contact" , "Leaf of book etc" , "Leaf - boy attendant" , "Side" , "Sheet of book" .)