Sign up for, as a contest (5)
I believe the answer is:
enter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sign up for as a contest</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for enter that I've seen before include "Come/go in" , "Pierce" , "Go/come in" , "Inscribe" , "Enroll, sign up" .)