The most common and most likely answer to this crossword clue is the 10 letter word MICROSCOPE
I've seen this crossword clue in The Daily Telegraph
M
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More clues leading to the result MICROSCOPE
- An eye for detail?
- Instrument not left over after more piccolos ordered
- Scientific tool that’s rewritten comic prose
- Dodgy crime scoop — it makes things seem bigger than they really are
- ‘Scientific Equipment Solved Crime!’ — scoop
- Very little opportunity for viewer?
- Little may be seen through it
- Instrument, one about to be included by new-style composer
- Viewer offering very little opportunity?
Buddy explains!

The straight part
We know that "viewer?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case viewer? = microscope.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 MICROSCOPE mean?
MICROSCOPE noun- An optical instrument used for observing small objects.
- Any instrument for imaging very small objects (such as an electron microscope).
- To examine with a microscope, to put under a microscope (literally or figuratively).