Horizontal beam (7)
(Other definitions for transom that I've seen before include "Lintel" , "Boat's flat stern - horizontal beam" , "Cross-member of boat or window" , "bolstering member" , "Crossbar over door" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">horizontal beam</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 lintel that I've seen before include "Supporting beam over a doorway" , "Horizontal beam over a doorway" , "Supporter" , "It's found above the door" , "Supporting member" .)