With such locks there's safety in numbers (11)
I believe the answer is:
combination
This clue could be a double definition.
'with such locks' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'safety in numbers' is the second definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'there's' is the link.
Can you help me to learn more?
(Other definitions for combination that I've seen before include "Union - coalescence" , "Mix" , "Mixture" , "Items joined together" , "Amalgamation" .)