Crosspiece on a ladder (4)
I believe the answer is:
rung
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crosspiece on a ladder</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 rung that I've seen before include "Crosspiece of a ladder" , "Telephoned" , "Phoned" , "Ladder's step" , "spoke" .)