The 28-year-old started out in the youth ranks at Arsenal and then had spells with Romford, Waltham Forest and East Thurrock United before joining Maidenhead for the first time in May 2013.
Clifton made eighty-two appearances for the Magpies, scoring 17 goals, in his first two-season spell at York Road, winning the managers` player of the year award in 2014 and finishing runner-up to Dave Tarpey for the supporters` vote in 2015.
A move to Havant & Waterlooville in the summer of 2015 was marred by injury and he returned to train with United this summer.
His performances in recent friendlies have earned him a deal for the new season.