creating a flat file (txt or excel) based on a query with one to many records

I am attempting to create a flat file that I need to send to a service
processor.
Problem
The file I am creating comes from a query with a one to many join. This
results in several records being reproduced for each entry in the many
table.
I need to append the unique information from the duplicate rows onto the end
of the initial record. In effect creating a record that can be exported in a
flat file as a single row.

I have scoured the access help and online resources and cannot find a
solution.

If someone can point me to a resource or example I can take it from there.

Thanks much for your help. First time poster.