How to use an external microphone without headphones on iPhone?

I have a condenser microphone to connect to my phone. I have a lightning port adapter and a combo audio adapter, but I don't want to use headphones. The intention is to have someone on face time with a group of people and put the microphone in the middle so the person on the phone can hear everyone better. But sound still needs to come out of the phone so we can hear her speaking. Is there a way I can do this?

[Re-Titled by Moderator]