Recruiting Guildford for his first Tahs squad is a major roll of the dice for Gibson, due to the winger's long history of trouble with alcohol.
Playing rugby in France was "too testing" for Guildford who returned home to Napier in May.
"Unfortunately couldn't return to my best rugby at Clermont and thought it was time to move on and be closer to family," Guildford said at the time. "Another opportunity for me to become fitter and mentally stronger. No point in thinking of what could of been, time to look to the future."
Guildford admitted in 2013 he was an alcoholic after a drunken assault at a party saw him enter a rehab facility to deal with longstanding issues on the booze.
Guildford's contrition and confrontation of his problems helped him narrowly avoid the sack by the New Zealand Rugby Union, who were fed up after years of alcohol-related incidents.