Number dash to secure E European espionage facility (4-6,4)

'espionage facility' is the definition.
(method of delivery used by spies)

'number dash to secure e european' is the wordplay.
I cannot quite see how this works, but
'number' could be 'l' (L is an example) and 'l' is found within the answer.
'dash' could be 'drop' (both can mean a very small amount of something) and 'drop' is found within the answer.
'e' is present in the answer.
'european' could be 'e' (abbreviation e.g. EU) and 'e' is found in the answer.
This may be the basis of the clue (or it may be nonsense).