be party to something

be (a) party to (something)

To be involved in something, often something clandestine. I refuse to be a party to your schemes any longer!
See also: party

be (a) ˈparty to something

(formal) take part in a (secret) plan, agreement, etc., and therefore be partly responsible for it: ‘Were you a party to this, Anna?’ ‘No, Mrs Jones, I was away on holiday at the time.’How many people were party to the plan?
See also: party, something