The most common and most likely answer to this crossword clue is the 3 plus 2 letter word POP UP
I've seen this crossword clue in The Daily Telegraph
P
O
P
U
P
More clues leading to the result POP UP
- Appear when parent has surfaced?
- Appear to get Dad out of bed
- Kind of toaster gets dad out of bed
- Appear unexpectedly from Towcester, say
- Make an appearance to call back operation on pressure increase
- Arrive with cracking report at university
- There’s pressure all around — work, you’re told it will appear suddenly
- Appear suddenly with report before judge
Buddy explains!

The straight part
We know that "Appear" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case appear = pop up.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does POP UP mean?
POP UP noun- Anything that pops up, particularly
- Coming into view suddenly from a concealed position.
- Opening out to form a three-dimensional structure when the page of a book is opened.
- Operating or existing for a brief period only; temporary.