Animal enclosure (3)
I think it could be either:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">animal enclosure</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 pen that I've seen before include "Small enclosure" , "Coop" , "Female swan" , "International Association of poets, playwrights etc" , "'The ... is mightier than the sword'" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">animal enclosure</span>' is the definition.<br/ ><span class="explanation-format__explanation">(pig sty)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sty that I've seen before include "Swinish place" , "Pig house" , "Farmyard enclosure" , "Hog house" , "Animal pen" .)