"Above his head at street level, he saw an angled aileron of ..." — A.S. Byatt quote meaning

Above his head at street level, he saw an angled aileron of a scarlet Porsche, its jaunty fin more or less at the upper edge of his window frame. A pair of very soft, clean glistening black shoes appeared, followed by impeccably creased matt charcoal pinstriped light woollen legs, followed by the beautifully cut lower hem of a jacket, its black vent revealing a scarlet silk lining, its open front revealing a flat muscular stomach under a finely-striped red and white shirt. Val’s legs followed, in powder-blue stockings and saxe-blue shoes, under the limp hem of a crêpey mustard-coloured dress, printed with blue moony flowers. The four feet advanced and retreated, retreated and advanced, the male feet insisting towards the basement stairs, the female feet resisting, parrying. Roland opened the door and went into the area, fired mostly by what always got him, pure curiosity as to what the top half looked like.