Clark incorporated many a cat into his paintings. Like chickens and dogs, cats are large enough to draw the eye serve as an anchor, or add a bit of interest to a composition, but small enough not to steal all of the focus. Of course in this picture from 1978, the cats are the entire focus. This scene of a mother and her kittens in the window of an abandoned house is from Southern Spain, and it evokes that region quite strongly. It's rustic, warm, and full of texture.
Clark included this painting in his book, A Gallery of Paintings. It is a lovely example of his work from that era, and it showcases all of his skill and technique - the subtle values, the play between tension (the mother cat) and relaxation (the kitten hanging out on the ledge). As an extra dramatic element, he has the kitten on the right seemingly about to pounce.