Register for (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">register for</span>' is the definition.<br/ ><span class="explanation-format__explanation">(as in registering for or entering a competition)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for enter that I've seen before include "Gain admission" , "put in for a race" , "Infiltrate" , "Record - stage direction - come in" , "Go/come in" .)
(Other definitions for enrol that I've seen before include "Sign on, register" , "Sign on, being a loner" , "Add to list of members" , "register for classes" , "Bring into service" .)
(Other definitions for sign up that I've seen before include "Enlist" , "Engage by written agreement" , "join the ranks" , "Commit to employment, education, etc" , "Take on" .)