Ask Clara to describe exactly what she's feeling?

The intensity of the... sexual urges lessened somewhat and the Doctor was able to think straight again. He took a deep breath and exhaled slowly.

"We need to discover what is going on here," he said at last. "I don't have much experience in these sort of... matters. Clara," he stood and leaned against the side of the tub, looking down into her eyes... her amazing, wonderful, gorgeous dark eyes. She really was quite gorgeous, and here she was sitting nude (well presumably nude as he couldn't really see anything under the bubbles except for the beautiful glistening wet skin of her face and shoulders and hands) in the tub in front of him with that cute half-smirk of hers. "I need you to tell me what you're feeling."

Clara nodded and thought for a moment. "Well, I'm feeling... flushed. At times overwhelmed and barely able to control my... myself."

"No, no, no!" the Doctor said, leaning back and sighing. "We're not going to get anywhere if we dilly-dally and weeble-wobble! We need to get right to the heart of it! I believe these feelings, these sexual urges are so strong because we are fighting them. I need to understand how intense they are for you. Don't be ashamed! Don't let your inhibitions hold you back. We need to get this all out in the open to fully understand and deal with it!"

"Alright, fine!" Clara said, determined. "I'm feeling horny, is that what you want to hear? I've never felt so hot and bothered in my life. I'm horny, horny, horny! My body is quaking ever since I arrived here. And the feeling is getting stronger by the minute!"

"Good, good," the Doctor said. "How does that make you feel? What does your body tell you?"

"I want to cum," Clara said after a pause. She had a slight twinkle in her eye now and she sat up slightly in the tub so that the suds now barely covered her breasts. "I want to cum so bad. And not just with my fingers. I've done that numerous times already and it doesn't help. I need to make love. No, forget that; I need to fuck. I need a nice hard, penis in my hands and in my mouth. I need a nice hard knob in my pussy, slow and hard and long. I want it in my bum. I need a proper bloody shag and a proper bloody rodgering!"

Her face was flushed now and she looked between the Doctor's legs. "Oh," she breathed.

The Doctor looked down too, and was surprised to see his fly was open and his erect manhood was in his hand. He was slowly stroking his full length and he was rock hard in his hand. He had no recollection at all of taking it out of his pants. He stopped masturbating at once and looked sheepish.

"No," Clara said, biting her lip. "Don't stop, Vance."

The Doctor began to stroke himself again with his left hand, and his right went into the water of the tub. Clara gasped when his hand touched her leg. He slid it up her smooth, wet skin, and her legs parted for him. He found her warmth; wet from the water and wet from her excitement. He slowly began to circle a finger around her erect clit and she gasped and arched her back. He hadn't much experience with this sort of thing, but was happy to note much of it came naturally.

"Yes," Clara breathed, her head tilted back and eyes closed. "This is what I need. Oh damn, this is what I need."