Closely follow (6)
I believe the answer is:
shadow
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">closely follow</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 shadow that I've seen before include "opposing counterpart" , "Reflected image" , "This opposition cabinet parallels the government" , "Inseparable follower" , "Follow closely; pale imitation" .)