The most common and most likely answer to this crossword clue is the 12 letter word SURVEILLANCE
I've seen this crossword clue in The Times
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More clues leading to the result SURVEILLANCE
Buddy explains!
The straight part
We know that "Watching" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case watching = surveillance.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 SURVEILLANCE mean?
SURVEILLANCE noun- Close observation of an individual or group; person or persons under suspicion.
- Continuous monitoring of disease occurrence for example.
- Systematic observation of places and people by visual, aural, electronic, photographic or other means.
- In criminal law, an investigation process by which police gather evidence about crimes, or suspected crime, through continued observation of persons or places.