Crop up (5)
I believe the answer is:
arise
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crop up</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 arise that I've seen before include "Happen" , "Originate; get up" , "Become apparent" , "Get to one's feet" , "Emerge" .)