Door frame piece (4)
I believe the answer is:
jamb
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">door frame piece</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for jamb that I've seen before include "Door, window side post" , "Side post of a doorway" , "Vertical side of a doorway" , "Door sidepiece" , "bit on the side?" .)