Mistakes - letting European escape - by British spies: they prompt reflections (7)
I believe the answer is:
mirrors
'reflections' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for mirrors that I've seen before include "Reflects" , "Reflective pieces of glass" , "Reflections" , "Shows a reflection" .)