Contained
I believe the answer is:
enclosed
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">contained</span>' is the definition.<br/ ><span class="explanation-format__explanation">(enclosing is a kind of containing)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for enclosed that I've seen before include "Surrounded on all sides" , "Surrounded completely, caged" , "Shut up or included in an envelope" , "Inserted with letter" , "Held" .)