England wing Henry Arundell scored a hat-trick on his Racing 92 debut in a 31-26 defeat at Toulon in the Top 14.
The 21-year-old joined after London Irish filed for administration in June.
The Rugby Football Union (RFU) and Premiership Rugby have a rule whereby players selected for England must compete in the Premiership.
Arundell was granted "special circumstances" to be eligible for the 2024 Six Nations because of short notice.
The pick of his three scores at Stade Mayol on Sunday was a trademark weaving run through the Toulon defence for his first try.
Arundell has scored seven tries in 10 appearances for England, including five on World Cup debut in the 71-0 group-stage win over Chile in September.
He did not feature again until the third-place play-off victory over Argentina.
Arundell is one of four members of the World Cup squad - alongside flanker Jack Willis, centre Joe Marchant and lock David Ribbans - playing in France.
He is in contention to be one of England's starting wingers in next year's Six Nations following Jonny May's retirement from international duty after the World Cup.