Complex sentence: This meant that his stage character was only partly inside the blackface minstrel tradition, and was using the tradition in a somewhat ironical manner; and indeed his material included cockney material as well as straightforward blackface songs and sketches.
Split into simpler sentences: This meant that his stage character was only partly inside the blackface minstrel tradition, and was using the tradition in a somewhat ironical manner. And indeed his material included cockney material as well as straightforward blackface songs and sketches.