Clifford, who joined the U's on loan last month, agreed an extension on Tuesday after an impressive spell in north Essex.
The Blues youth product, who has made five appearances so far, is now looking forward to the rest of the campaign.
"I've spoken to the gaffer here and to people at Chelsea and they've been really happy with how I've been doing," he told the club's official website.
"It has been a really good experience so far. The gaffer has been fantastic to me and the players have as well, so I'm glad that I took the chance to come here.
"This has definitely been the right move for me, and it has been a chance to experience life away from Chelsea, to play games and experience living with another team mate and I think I've coped well so far."
He added: "Physically, I feel better than I have been before and I can't wait to attack the rest of the games in front of us."