Complex sentence: He had signed with Jokerit for the 2005--06 season, but the contract had a clause enabling him to return to the NHL, and when the Oilers offered him a one-year contract in August 2005, Rita signed on to return to North America.
Split into simpler sentences: He had signed with Jokerit for the 2005--06 season with a contractual clause enabling him to return to the NHL. When the Oilers offered him a one-year contract in August 2005, Rita signed on to return to North America.