Complex sentence: Spence joined the Progressive Unionist Party (PUP), becoming a leading figure in the group and as a PUP representative he took a principal role in delivering the loyalist ceasefires of 1994.
Split into simpler sentences: Spence joined the Progressive Unionist Party (PUP), becoming a leading figure in the group. As a PUP representative he took a principal role in delivering the loyalist ceasefires of 1994.