Together with centre-back partner Chris Timons, Ellender joined Altrincham in 1998, and helped the club win the Northern Premier League title and gain promotion to the Conference. He was sold to fellow Conference club Scarborough in November 1999. In 2001 Ellender signed for Boston United for £80,000, which was the club's record transfer fee. He went on to captain Boston to the Conference title and promotion to the Football League in 2001–02, and remained with the club until 2008. He was loaned to Chester City in February 2006 for the remainder of the season, but was recalled a month later because of injuries among Boston defenders.
After seven years with Boston, during which time he played 275 games in all competitions, and, according to the club's website, "endeared himself to the club's supporters with a never-say-die attitude", he moved on to Alfreton Town, but re-signed for Boston United on loan in March 2009. At the end of the season, neither Boston nor Alfreton offered him a contract, and he joined Retford United for the 2009–10 season. He joined North Ferriby United during the summer of 2010.