She said Clifford locked the door of his office and kept saying how "turned on" he was as he carried out the attack.
The woman, one of seven alleged victims of indecent assault by Clifford, told London's Southwark Crown Court that she was advised to go to see him in 1983, when she was about 17.
Clifford told her how important he was to the press, how he made people's careers, and that he had had sex with Diana Ross, she said. "For me, Diana Ross was a very beautiful, famous woman, I couldn't imagine why she would sleep with him," she said.
Clifford told her that she needed to get some publicity, and it was very important she was seen with the right person.
She said: "I thought, this is not what I want to be involved in, I couldn't think of anything worse than being in the papers, or being on TV, I wanted to be a fashion model."
He said he wanted to see her figure and told her to take her dress off. The woman, who is now 48, rang police when she saw Clifford had been arrested.
Clifford, 70, from Hersham in Surrey, is accused of 11 counts of indecent assault against seven women and girls. He denies all charges.
The trial continues.