Toe the line (4)
I believe the answer is:
obey
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">toe the line</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for obey that I've seen before include "Comply with orders" , "Accept instructions" , "Be dominated" , "Hear" , "Do as ordered" .)