The most common and most likely answer to this crossword clue is the 6 plus 4 letter word DOUBLE TAKE
I've seen this crossword clue in Independent
D
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More clues leading to the result DOUBLE TAKE
- Jacket nude stripped off, generating surprised reaction
- Delayed reaction after greatly increased receipts
- Greatly increase receipts: that brings surprised reaction
- Delayed reaction appropriate after image
- Delayed action with stand-in starting film scene
- Shocked response from one of a pair rankles
- Delayed action with stand-in starting film scene?
- Shocked look is what Betty and Scott have, stripped naked
Buddy explains!

The straight part
We know that "surprised reaction" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case surprised reaction = double take.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.