The Doctor worked quickly he ran down the street looking for something that might put a dent in a 400 foot bipedal lizard. He tore at electrical conduit with his sonic screwdriver, removing a small transmission dish off of a news van. Not ideal, but it would have to do. He needed power and a LOT of it. If the City was going to throw things like this into the mix, it called for drastic measures.
"It worked against Daleks" he commented, as the dish was wired into the roof of the TARDIS. Turning the Sonic Screwdriver to full power, the dish amplified a piercing sonic wave at the horror rampaging in the City.
Waving his arms and screaming, "Come on you overgrown iguana! come pick on something your own size!" The Doctor hoped drawing this beastie away would work.