The jury in the sexual assault trial of the publicist Max Clifford was instructed to "settle down and remember where you are" by the judge after they burst into laughter while hearing evidence.

Southwark crown court heard that Clifford groped a teenage model who went to him for career advice, telling her she could get a part in a James Bond film - but she might have to sleep with the producer, Cubby Broccoli.

She said Clifford locked the door of his office and he kept saying how "turned on" he was as he carried out the assault.

The woman, one of seven alleged victims of indecent assault by Clifford, told the jury she was advised 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.

The jury heard that Clifford told her to take her dress off, which she did reluctantly as she was wearing a thermal vest and her tights had holes in. Clifford was "overcome", saying how turned on he was, she said: "It was the tights, he was absolutely riveted about the tights."

The woman then alleged Clifford groped her chest and arms – "At this point I'm feeling utterly stupid, totally in shock, I'm just not doing anything" – and masturbated while he was on the phone to his wife. She said she felt wet on her breastbone area, and presumed Clifford had ejaculated.

Clifford then told her he wanted her to come to dinner with him and his wife and Cubby Broccoli, and masturbate him under the table while he sat next to his wife, the woman said.

"Then he went on to say I may need to sleep with Cubby Broccoli, but I would get a part in a Bond film. "I loathe James Bond films."

The woman said she went back to her hotel and stayed in bed for a number of days, telling only her sister and some friends what had happened.

The woman, now 48, rang police when she saw Clifford had been arrested.

Clifford, from Hersham in Surrey, is accused of 11 counts of indecent assault against seven women and girls. He denies all the charges.

The woman said in her evidence she thought Clifford was well-endowed and his penis was very large. "I had only seen one before, I had never seen one in that proximity and that situation."

The court has heard claims that his penis is "tiny" and no more than two-and-a-half inches when erect. When Richard Horwell QC, defending, asked her about the issue, the woman remarked: "I have a small mouth. I do, my dentist has always said."

This prompted laughter on the jury, which was sent out for a few minutes. Jurors returned to be told by judge Anthony Leonard QC: "It is inevitable in a case dealing with this sort of graphic detail that members of the jury want to burst out laughing.

"I can remember a very boring court case and we – I wasn't a judge then – became helpless with laughter and the judge had tears in his eyes and it took over 25 minutes to recover.

"But we have got to remember that this is a court of law and we are dealing with serious allegations, and, in fairness to the witness, and the rest of the court, you have got to learn not to react to what's happening. Can I ask you to settle down and remember where you are?"

Horwell suggested to the woman that her description of the alleged events was invention and fantasy, and she said: "Absolutely not."

Asked by Rosina Cottage QC, prosecuting, if she had lied, she said: "Oh no, it's crystal clear."

The trial continues.