Chris Willman Music WriterCowboy Jack Clement, legendary in music circles for everything from being present at the birth of rock ‘n’ roll at Sun Studios to writing hits for Johnny Cash to eventually working with U2, has been pegged as the subject of a feature film that Nashville’s Visionary Media Group has signed a deal with Clement’s estate to develop.Additionally, plans are afoot for an all-star album that would have singers and songwriters that knew Clement finishing and recording unfinished