Fail to mention (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fail to mention</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 omit that I've seen before include "Miss out" , "Disregard" , "Leave out or fail to do" , "Fail to mention" , "Exclude - neglect" .)