without any others being included or involved; "was entirely to blame"; "a school devoted entirely to the needs of problem children"; "he works for Mr Smith exclusively"; "did it solely for money"; "the burden of proof rests on the prosecution alone"; "a privilege granted only to him"
If something involves solely one thing, it involves only this thing and no others. This program is a production of NPR, which is solely responsible for its content. not involving anything or anyone else = only