Appear unexpectedly (4,2)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">appear unexpectedly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for pop up that I've seen before include "Appear suddenly or unexpectedly" , "three-dimensional picture book" , "which may interrupt computer user" , "Appear (like toast?)" , "book for youngster" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">appear unexpectedly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for crop up that I've seen before include "Occur unexpectedly - as part of harvest?" , "Appear unexpectedly" , "Occur, arise" , "Occur by chance - like harvest?" , "Occur unexpectedly - like harvest?" .)
(Another definition for popup that I've seen is " What 11 [TOAST] might do".)