Saboteur opens secret letters here (6)
I believe the answer is:
europe
'secret letters here' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'saboteur opens' is the wordplay.
'EUROPE' is hidden within the letters.
But, I am not sure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for europe that I've seen before include "Union in popular parlance?" , "O, puree on the continent" , "Continent 6)" , "our part of the world" , "Second-smallest continent" .)