Head Coach Richard Hill said: "We are very excited that Jon will be joining us next season. He is vastly experienced and has been playing at one of the top clubs in the country for many seasons. He is physically a very powerful man and has the ability to offload and break the advantage line. Jon is a multi-skilled player, as he can operate at 12, 13 or 15, and will add a great deal to our midfield options."
Clarke said: "This is a new challenge for me as I prepare to move to a new club after a long and hugely enjoyable spell at Northampton. I felt I needed a change and I spoke to Richard Hill and was really impressed by his vision and also the set-up at the club. I feel I can play a role in the club moving up another level."