The most common and most likely answer to this crossword clue is the 8 letter word SURPRISE
I've seen this crossword clue in The Guardian
S
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P
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More clues leading to the result SURPRISE
- Heard knight got award for a Haydn symphony
- Unexpected gentleman becomes over-curious, we hear
- Hit for six? Super – sir’s out
- Drink noisily, tossing off a litre — get up, then stagger
- Firm adopting advertising is showing incredulity
- Certainly, spin is bound to shock
- Unexpected growth following insurance company’s setback
- Gentleman’s award is reported with amazement
- Unexpected teacher is being nosy, reportedly
- Astonishment over American priest discovered in tower
Buddy explains!

The straight part
We know that "Unexpected" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unexpected = surprise.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 SURPRISE mean?
SURPRISE noun- Something unexpected.
- The feeling that something unexpected has happened.
- A dish covered with a crust of raised pastry, but with no other contents.
- To cause (someone) to feel unusually alarmed or delighted by something unexpected.
- To do something to (a person) that they are not expecting, as a surprise.
- To undergo or witness something unexpected.
- To cause surprise.
- To attack unexpectedly.
- To take unawares.