have an in with someone—(coll.) have influence with smb. of authority:
- He had an in with the city government, but that doesn’t mean they knew everything he did.
Note: The expression does not correlate in meaning with the phrase have a run-in with someone—(coll.) have a troublesome encounter or a row with a person:
- Your father and I have many run-ins these days. He can’t get it into his thick skull that I have come of age.
have it in for someone—show ill will towards smb.; intend to do harm to a person:
- I just don’t want to lose my funding because she has it in for me badmouthing me to everyone in the department.
See also: be in with someone / be with someone.