There are a number of idioms around the string, that carry the idea that if one pulls it, other things will (or will not) come with it:
with (no) strings attached
have the world on the string
Conversely, is there an idiom to describe this metaphoric string (contract clause, pressure tactic, discovery) that leads to other things?
This clause in the contract is the --- that you should watch for.
This discovery is the --- that will lead to many other ones.