The most common and most likely answer to this crossword clue is the 5 letter word SPIES
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The straight part
We know that "Sees" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sees = spies.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 SPIES mean?
SPIES noun- A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage).
- To act as a spy.
- To spot; to catch sight of.
- To search narrowly; to scrutinize.
- To explore; to see; to view; inspect and examine secretly, as a country.