Complex sentence: He is best known for his 12-year tenure working for Total Nonstop Action Wrestling (TNA) from 2004-2016, Young has since been performing in WWE NXT, despite not being officially signed to a WWE contract.
Split into simpler sentences: He is best known for his 12-year tenure working for Total Nonstop Action Wrestling (TNA) from 2004-2016. Following his departure from TNA, Young has since been performing in WWE NXT, despite not being officially signed to a WWE contract.