ring in

ring in  {v. phr.},  {informal}

1. To bring in (someone or something) from the outside dishonestly or without telling; often: hire and introduce under a false name.

Bob offered to ring him in on the party by pretending he was a cousin from out of town.

No wonder their team beat us; they rang in a professional to pitch for them under the name of Dan Smith.

2. To ring a special clock that records the time you work.